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\newcommand{\titre}{Le car de ramassage}
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    \small Un car de ramassage doit s'arrêter à chaque carrefour d'un quartier, une fois et une seule. Selon le plan c'est possible ou non — et un simple coloriage permet souvent de le dire d'avance, sans essayer.
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\end{center}
\noindent \textbf{Le car part de l'école, au carrefour M, et doit s'arrêter à chaque carrefour exactement une fois.} Il emprunte les rues qu'il veut et n'a pas à toutes les parcourir.\par\addvspace{0.35em}
\begin{center}
\renewcommand{\arraystretch}{1.35}
\begin{tabular}{|c|c|c|c|}
\hline
\cellcolor{black!32}\bfseries Les rues & ⑩ chemin de Ronde & Ⓑ Place de l'Église & Ⓛ Place du Vieux-Puits \\ \hline
① impasse du Puits & ⑪ rue Pasteur & Ⓒ Rond-point du Pont & Ⓜ Carrefour du Moulin \\ \hline
② impasse Sainte-Anne & ⑫ sentier des Prés & Ⓓ Carrefour des Tilleuls & \cellcolor{black!32}\bfseries Les bâtiments \\ \hline
③ rue du Four & ⑬ allée des Peupliers & Ⓔ Carrefour de la Mairie & \textbf{a} l'école \\ \hline
④ rue des Lilas & ⑭ chemin des Vignes & Ⓕ Rond-point des Vaches & \textbf{b} la bibliothèque \\ \hline
⑤ rue de l'Église & ⑮ passage du Marché & Ⓖ Rond-point de la Gare & \textbf{c} le gymnase \\ \hline
⑥ allée des Tilleuls & ⑯ rue Haute & Ⓗ Fontaine Notre-Dame & \textbf{d} la salle des fêtes \\ \hline
⑦ rue de la Mairie & ⑰ rue du Moulin & Ⓘ Rond-point du Stade &  \\ \hline
⑧ rue du Stade & \cellcolor{black!32}\bfseries Les carrefours & Ⓙ Carrefour de l'Hôpital &  \\ \hline
⑨ rue des Écoles & Ⓐ Coin du Lavoir & Ⓚ Place des Tanneurs &  \\ \hline
\end{tabular}
\end{center}
\noindent{\small\itshape Légende du plan}\par\addvspace{0.4em}
\begin{enumerate}
  \item Colorier les carrefours du plan avec \textbf{deux couleurs}, de sorte que deux carrefours \textbf{reliés par une rue} ne soient jamais de la même couleur. Combien y en a-t-il de chaque couleur ?
  \item Le car roule d'un carrefour au suivant. Que peut-on dire de la \textbf{couleur} des arrêts successifs ? Qu'en déduire sur les couleurs des arrêts d'une tournée qui les dessert tous ?
  \item \textbf{Le car peut-il desservir tous les carrefours, une fois chacun, et revenir à l'école ?} Si oui, décrire un trajet ; sinon, démontrer que c'est impossible.
  \item \textbf{Et s'il n'est pas obligé de revenir à l'école ?} Même consigne.
\end{enumerate}
\newpage
\section*{\textcolor{red}{Correction}}
\needspace{5\baselineskip}
\subsection*{\textcolor{red}{Le car de ramassage — Correction}}
\needspace{3\baselineskip}
\begin{center}
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\draw[line width=0.5pt] (1.604,5.191) -- (1.801,5.207) -- (1.998,5.218) -- (2.195,5.225) -- (2.393,5.228) -- (2.59,5.225) -- (2.788,5.218) -- (2.985,5.207) -- (3.182,5.19) -- (3.378,5.17) -- (3.574,5.144) -- (3.769,5.114) -- (3.964,5.079) -- (4.157,5.04) -- (4.35,4.996);
\draw[line width=0.5pt] (4.35,4.996) -- (4.624,4.997) -- (4.898,5.004) -- (5.171,5.017) -- (5.445,5.037) -- (5.718,5.064) -- (5.99,5.096) -- (6.261,5.136) -- (6.532,5.181) -- (6.801,5.233) -- (7.069,5.291) -- (7.336,5.356) -- (7.6,5.426) -- (7.863,5.503) -- (8.124,5.586);
\draw[line width=0.5pt] (4.35,4.996) -- (4.422,4.815) -- (4.49,4.631) -- (4.553,4.446) -- (4.612,4.26) -- (4.667,4.072) -- (4.717,3.883) -- (4.763,3.692) -- (4.804,3.501) -- (4.841,3.309) -- (4.873,3.116) -- (4.901,2.922) -- (4.924,2.728) -- (4.943,2.533) -- (4.957,2.338);
\draw[line width=0.5pt] (11.353,4.852) -- (11.315,4.658) -- (11.282,4.463) -- (11.253,4.267) -- (11.229,4.071) -- (11.21,3.874) -- (11.195,3.677) -- (11.185,3.48) -- (11.18,3.282) -- (11.179,3.084) -- (11.183,2.886) -- (11.191,2.689) -- (11.204,2.491) -- (11.222,2.295) -- (11.245,2.098);
\draw[line width=0.5pt] (4.957,2.338) -- (5.16,2.34) -- (5.364,2.337) -- (5.567,2.33) -- (5.77,2.317) -- (5.973,2.3) -- (6.176,2.278) -- (6.378,2.251) -- (6.579,2.219) -- (6.78,2.183) -- (6.979,2.142) -- (7.178,2.096) -- (7.375,2.046) -- (7.571,1.991) -- (7.766,1.932);
\draw[line width=0.5pt] (7.766,1.932) -- (8.014,1.905) -- (8.263,1.885) -- (8.512,1.87) -- (8.762,1.862) -- (9.012,1.859) -- (9.262,1.862) -- (9.512,1.871) -- (9.762,1.886) -- (10.011,1.907) -- (10.259,1.934) -- (10.507,1.966) -- (10.754,2.004) -- (11.0,2.048) -- (11.245,2.098);
\filldraw[fill=white, draw=black, line width=0.5pt] (1.859,11.73) -- (1.831,11.873) -- (1.75,11.994) -- (1.629,12.074) -- (1.486,12.103) -- (1.343,12.074) -- (1.222,11.994) -- (1.141,11.873) -- (1.113,11.73) -- (1.141,11.587) -- (1.222,11.466) -- (1.343,11.385) -- (1.486,11.356) -- (1.629,11.385) -- (1.75,11.466) -- (1.831,11.587) -- cycle;
\filldraw[fill=black!38, draw=black, line width=0.5pt] (11.289,10.795) -- (11.26,10.938) -- (11.18,11.059) -- (11.058,11.14) -- (10.916,11.168) -- (10.773,11.14) -- (10.652,11.059) -- (10.571,10.938) -- (10.542,10.795) -- (10.571,10.652) -- (10.652,10.531) -- (10.773,10.45) -- (10.916,10.422) -- (11.058,10.45) -- (11.18,10.531) -- (11.26,10.652) -- cycle;
\filldraw[fill=white, draw=black, line width=0.5pt] (5.404,8.568) -- (5.375,8.711) -- (5.294,8.832) -- (5.173,8.913) -- (5.03,8.941) -- (4.887,8.913) -- (4.766,8.832) -- (4.686,8.711) -- (4.657,8.568) -- (4.686,8.425) -- (4.766,8.304) -- (4.887,8.223) -- (5.03,8.194) -- (5.173,8.223) -- (5.294,8.304) -- (5.375,8.425) -- cycle;
\filldraw[fill=black!38, draw=black, line width=0.5pt] (1.726,8.084) -- (1.698,8.227) -- (1.617,8.348) -- (1.496,8.429) -- (1.353,8.458) -- (1.21,8.429) -- (1.089,8.348) -- (1.008,8.227) -- (0.98,8.084) -- (1.008,7.942) -- (1.089,7.821) -- (1.21,7.74) -- (1.353,7.711) -- (1.496,7.74) -- (1.617,7.821) -- (1.698,7.942) -- cycle;
\filldraw[fill=black!38, draw=black, line width=0.5pt] (8.384,7.836) -- (8.355,7.978) -- (8.274,8.1) -- (8.153,8.18) -- (8.01,8.209) -- (7.868,8.18) -- (7.747,8.1) -- (7.666,7.978) -- (7.637,7.836) -- (7.666,7.693) -- (7.747,7.572) -- (7.868,7.491) -- (8.01,7.462) -- (8.153,7.491) -- (8.274,7.572) -- (8.355,7.693) -- cycle;
\filldraw[fill=white, draw=black, line width=0.5pt] (11.147,7.809) -- (11.119,7.952) -- (11.038,8.073) -- (10.917,8.154) -- (10.774,8.182) -- (10.631,8.154) -- (10.51,8.073) -- (10.429,7.952) -- (10.401,7.809) -- (10.429,7.666) -- (10.51,7.545) -- (10.631,7.464) -- (10.774,7.436) -- (10.917,7.464) -- (11.038,7.545) -- (11.119,7.666) -- cycle;
\filldraw[fill=white, draw=black, line width=0.5pt] (8.498,5.586) -- (8.469,5.729) -- (8.388,5.85) -- (8.267,5.931) -- (8.124,5.96) -- (7.982,5.931) -- (7.861,5.85) -- (7.78,5.729) -- (7.751,5.586) -- (7.78,5.444) -- (7.861,5.322) -- (7.982,5.242) -- (8.124,5.213) -- (8.267,5.242) -- (8.388,5.322) -- (8.469,5.444) -- cycle;
\filldraw[fill=white, draw=black, line width=0.5pt] (1.977,5.191) -- (1.949,5.333) -- (1.868,5.454) -- (1.747,5.535) -- (1.604,5.564) -- (1.461,5.535) -- (1.34,5.454) -- (1.259,5.333) -- (1.231,5.191) -- (1.259,5.048) -- (1.34,4.927) -- (1.461,4.846) -- (1.604,4.817) -- (1.747,4.846) -- (1.868,4.927) -- (1.949,5.048) -- cycle;
\filldraw[fill=black!38, draw=black, line width=0.5pt] (4.723,4.996) -- (4.695,5.139) -- (4.614,5.26) -- (4.493,5.341) -- (4.35,5.37) -- (4.207,5.341) -- (4.086,5.26) -- (4.005,5.139) -- (3.976,4.996) -- (4.005,4.854) -- (4.086,4.732) -- (4.207,4.652) -- (4.35,4.623) -- (4.493,4.652) -- (4.614,4.732) -- (4.695,4.854) -- cycle;
\filldraw[fill=black!38, draw=black, line width=0.5pt] (11.726,4.852) -- (11.698,4.995) -- (11.617,5.116) -- (11.496,5.197) -- (11.353,5.225) -- (11.21,5.197) -- (11.089,5.116) -- (11.008,4.995) -- (10.98,4.852) -- (11.008,4.709) -- (11.089,4.588) -- (11.21,4.507) -- (11.353,4.479) -- (11.496,4.507) -- (11.617,4.588) -- (11.698,4.709) -- cycle;
\filldraw[fill=white, draw=black, line width=0.5pt] (5.33,2.338) -- (5.301,2.481) -- (5.221,2.602) -- (5.099,2.683) -- (4.957,2.712) -- (4.814,2.683) -- (4.693,2.602) -- (4.612,2.481) -- (4.583,2.338) -- (4.612,2.196) -- (4.693,2.075) -- (4.814,1.994) -- (4.957,1.965) -- (5.099,1.994) -- (5.221,2.075) -- (5.301,2.196) -- cycle;
\filldraw[fill=white, draw=black, line width=0.5pt] (11.618,2.098) -- (11.589,2.241) -- (11.509,2.362) -- (11.387,2.443) -- (11.245,2.471) -- (11.102,2.443) -- (10.981,2.362) -- (10.9,2.241) -- (10.871,2.098) -- (10.9,1.955) -- (10.981,1.834) -- (11.102,1.753) -- (11.245,1.725) -- (11.387,1.753) -- (11.509,1.834) -- (11.589,1.955) -- cycle;
\filldraw[fill=black!38, draw=black, line width=0.5pt] (8.139,1.932) -- (8.11,2.074) -- (8.029,2.195) -- (7.908,2.276) -- (7.766,2.305) -- (7.623,2.276) -- (7.502,2.195) -- (7.421,2.074) -- (7.392,1.932) -- (7.421,1.789) -- (7.502,1.668) -- (7.623,1.587) -- (7.766,1.558) -- (7.908,1.587) -- (8.029,1.668) -- (8.11,1.789) -- cycle;
\filldraw[fill=white, draw=black, line width=0.5pt] (1.653,9.514) -- (1.772,9.533) -- (1.879,9.587) -- (1.964,9.672) -- (2.019,9.78) -- (2.038,9.898) -- (2.019,10.017) -- (1.964,10.125) -- (1.879,10.21) -- (1.772,10.264) -- (1.653,10.283) -- (1.653,10.283) -- (1.535,10.264) -- (1.427,10.21) -- (1.342,10.125) -- (1.288,10.017) -- (1.269,9.898) -- (1.288,9.78) -- (1.342,9.672) -- (1.427,9.587) -- (1.535,9.533) -- (1.653,9.514) -- cycle;
\node at (1.653,9.898) {\scalebox{1.614}{\small 1}};
\filldraw[fill=white, draw=black, line width=0.5pt] (11.352,8.893) -- (11.471,8.912) -- (11.578,8.967) -- (11.663,9.052) -- (11.718,9.159) -- (11.737,9.278) -- (11.718,9.397) -- (11.663,9.504) -- (11.578,9.589) -- (11.471,9.644) -- (11.352,9.662) -- (11.352,9.662) -- (11.233,9.644) -- (11.126,9.589) -- (11.041,9.504) -- (10.987,9.397) -- (10.968,9.278) -- (10.987,9.159) -- (11.041,9.052) -- (11.126,8.967) -- (11.233,8.912) -- (11.352,8.893) -- cycle;
\node at (11.352,9.278) {\scalebox{1.614}{\small 2}};
\filldraw[fill=white, draw=black, line width=0.5pt] (6.582,8.068) -- (6.701,8.086) -- (6.808,8.141) -- (6.893,8.226) -- (6.948,8.333) -- (6.966,8.452) -- (6.948,8.571) -- (6.893,8.678) -- (6.808,8.763) -- (6.701,8.818) -- (6.582,8.837) -- (6.582,8.837) -- (6.463,8.818) -- (6.356,8.763) -- (6.271,8.678) -- (6.216,8.571) -- (6.197,8.452) -- (6.216,8.333) -- (6.271,8.226) -- (6.356,8.141) -- (6.463,8.086) -- (6.582,8.068) -- cycle;
\node at (6.582,8.452) {\scalebox{1.614}{\small 3}};
\filldraw[fill=white, draw=black, line width=0.5pt] (5.215,6.297) -- (5.334,6.316) -- (5.441,6.371) -- (5.526,6.456) -- (5.581,6.563) -- (5.6,6.682) -- (5.581,6.801) -- (5.526,6.908) -- (5.441,6.993) -- (5.334,7.048) -- (5.215,7.066) -- (5.215,7.066) -- (5.096,7.048) -- (4.989,6.993) -- (4.904,6.908) -- (4.849,6.801) -- (4.831,6.682) -- (4.849,6.563) -- (4.904,6.456) -- (4.989,6.371) -- (5.096,6.316) -- (5.215,6.297) -- cycle;
\node at (5.215,6.682) {\scalebox{1.614}{\small 4}};
\filldraw[fill=white, draw=black, line width=0.5pt] (3.161,8.171) -- (3.28,8.19) -- (3.387,8.245) -- (3.472,8.33) -- (3.527,8.437) -- (3.546,8.556) -- (3.527,8.674) -- (3.472,8.782) -- (3.387,8.867) -- (3.28,8.921) -- (3.161,8.94) -- (3.161,8.94) -- (3.043,8.921) -- (2.935,8.867) -- (2.85,8.782) -- (2.796,8.674) -- (2.777,8.556) -- (2.796,8.437) -- (2.85,8.33) -- (2.935,8.245) -- (3.043,8.19) -- (3.161,8.171) -- cycle;
\node at (3.161,8.556) {\scalebox{1.614}{\small 5}};
\filldraw[fill=white, draw=black, line width=0.5pt] (1.981,6.297) -- (2.1,6.315) -- (2.207,6.37) -- (2.292,6.455) -- (2.347,6.562) -- (2.365,6.681) -- (2.347,6.8) -- (2.292,6.907) -- (2.207,6.992) -- (2.1,7.047) -- (1.981,7.066) -- (1.981,7.066) -- (1.862,7.047) -- (1.755,6.992) -- (1.67,6.907) -- (1.615,6.8) -- (1.596,6.681) -- (1.615,6.562) -- (1.67,6.455) -- (1.755,6.37) -- (1.862,6.315) -- (1.981,6.297) -- cycle;
\node at (1.981,6.681) {\scalebox{1.614}{\small 6}};
\filldraw[fill=white, draw=black, line width=0.5pt] (9.395,7.708) -- (9.514,7.727) -- (9.621,7.782) -- (9.706,7.867) -- (9.761,7.974) -- (9.779,8.093) -- (9.761,8.212) -- (9.706,8.319) -- (9.621,8.404) -- (9.514,8.458) -- (9.395,8.477) -- (9.395,8.477) -- (9.276,8.458) -- (9.169,8.404) -- (9.084,8.319) -- (9.029,8.212) -- (9.01,8.093) -- (9.029,7.974) -- (9.084,7.867) -- (9.169,7.782) -- (9.276,7.727) -- (9.395,7.708) -- cycle;
\node at (9.395,8.093) {\scalebox{1.614}{\small 7}};
\filldraw[fill=white, draw=black, line width=0.5pt] (8.544,6.351) -- (8.663,6.369) -- (8.77,6.424) -- (8.855,6.509) -- (8.91,6.616) -- (8.929,6.735) -- (8.91,6.854) -- (8.855,6.961) -- (8.77,7.046) -- (8.663,7.101) -- (8.544,7.12) -- (8.544,7.12) -- (8.425,7.101) -- (8.318,7.046) -- (8.233,6.961) -- (8.179,6.854) -- (8.16,6.735) -- (8.179,6.616) -- (8.233,6.509) -- (8.318,6.424) -- (8.425,6.369) -- (8.544,6.351) -- cycle;
\node at (8.544,6.735) {\scalebox{1.614}{\small 8}};
\filldraw[fill=white, draw=black, line width=0.5pt] (11.319,5.996) -- (11.438,6.015) -- (11.545,6.069) -- (11.63,6.154) -- (11.685,6.262) -- (11.703,6.38) -- (11.685,6.499) -- (11.63,6.606) -- (11.545,6.691) -- (11.438,6.746) -- (11.319,6.765) -- (11.319,6.765) -- (11.2,6.746) -- (11.093,6.691) -- (11.008,6.606) -- (10.953,6.499) -- (10.934,6.38) -- (10.953,6.262) -- (11.008,6.154) -- (11.093,6.069) -- (11.2,6.015) -- (11.319,5.996) -- cycle;
\node at (11.319,6.38) {\scalebox{1.614}{\small 9}};
\filldraw[fill=white, draw=black, line width=0.5pt] (9.865,4.593) -- (9.983,4.612) -- (10.091,4.666) -- (10.176,4.751) -- (10.23,4.859) -- (10.249,4.977) -- (10.23,5.096) -- (10.176,5.203) -- (10.091,5.288) -- (9.983,5.343) -- (9.865,5.362) -- (9.503,5.362) -- (9.384,5.343) -- (9.277,5.288) -- (9.192,5.203) -- (9.137,5.096) -- (9.118,4.977) -- (9.137,4.859) -- (9.192,4.751) -- (9.277,4.666) -- (9.384,4.612) -- (9.503,4.593) -- cycle;
\node at (9.684,4.977) {\scalebox{1.614}{\small 10}};
\filldraw[fill=white, draw=black, line width=0.5pt] (8.358,3.352) -- (8.477,3.37) -- (8.584,3.425) -- (8.669,3.51) -- (8.724,3.617) -- (8.742,3.736) -- (8.724,3.855) -- (8.669,3.962) -- (8.584,4.047) -- (8.477,4.102) -- (8.358,4.121) -- (7.996,4.121) -- (7.877,4.102) -- (7.77,4.047) -- (7.685,3.962) -- (7.63,3.855) -- (7.611,3.736) -- (7.63,3.617) -- (7.685,3.51) -- (7.77,3.425) -- (7.877,3.37) -- (7.996,3.352) -- cycle;
\node at (8.177,3.736) {\scalebox{1.614}{\small 11}};
\filldraw[fill=white, draw=black, line width=0.5pt] (3.193,5.206) -- (3.312,5.225) -- (3.419,5.279) -- (3.504,5.364) -- (3.559,5.471) -- (3.578,5.59) -- (3.559,5.709) -- (3.504,5.816) -- (3.419,5.901) -- (3.312,5.956) -- (3.193,5.975) -- (2.831,5.975) -- (2.712,5.956) -- (2.605,5.901) -- (2.52,5.816) -- (2.465,5.709) -- (2.447,5.59) -- (2.465,5.471) -- (2.52,5.364) -- (2.605,5.279) -- (2.712,5.225) -- (2.831,5.206) -- cycle;
\node at (3.012,5.59) {\scalebox{1.614}{\small 12}};
\filldraw[fill=white, draw=black, line width=0.5pt] (6.383,5.131) -- (6.502,5.15) -- (6.609,5.204) -- (6.694,5.29) -- (6.749,5.397) -- (6.768,5.516) -- (6.749,5.634) -- (6.694,5.742) -- (6.609,5.827) -- (6.502,5.881) -- (6.383,5.9) -- (6.021,5.9) -- (5.902,5.881) -- (5.795,5.827) -- (5.71,5.742) -- (5.655,5.634) -- (5.637,5.516) -- (5.655,5.397) -- (5.71,5.29) -- (5.795,5.204) -- (5.902,5.15) -- (6.021,5.131) -- cycle;
\node at (6.202,5.516) {\scalebox{1.614}{\small 13}};
\filldraw[fill=white, draw=black, line width=0.5pt] (5.319,3.394) -- (5.437,3.412) -- (5.545,3.467) -- (5.63,3.552) -- (5.684,3.659) -- (5.703,3.778) -- (5.684,3.897) -- (5.63,4.004) -- (5.545,4.089) -- (5.437,4.144) -- (5.319,4.163) -- (4.957,4.163) -- (4.838,4.144) -- (4.731,4.089) -- (4.646,4.004) -- (4.591,3.897) -- (4.572,3.778) -- (4.591,3.659) -- (4.646,3.552) -- (4.731,3.467) -- (4.838,3.412) -- (4.957,3.394) -- cycle;
\node at (5.138,3.778) {\scalebox{1.614}{\small 14}};
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\noindent{\small\itshape Deux carrefours reliés par une rue n'ont jamais la même couleur.}\par\addvspace{0.4em}
\noindent \textbf{1.} Le coloriage est \textbf{forcé} : une fois la couleur d'un carrefour choisie, celle de tous les autres suit, de proche en proche.\par\addvspace{0.35em}
\begin{center}
\renewcommand{\arraystretch}{1.35}
\begin{tabular}{|c|c|c|}
\hline
\cellcolor{blue!7}\bfseries Couleur & \cellcolor{blue!7}\bfseries Carrefours & \cellcolor{blue!7}\bfseries Nombre \\ \hline
sombres & B, D, E, I, J, M & 6 \\ \hline
clairs & A, C, F, G, H, K, L & 7 \\ \hline
\end{tabular}
\end{center}
\noindent{\color{red!80!black}\bfseries Il y a \textbf{6} carrefours sombres et \textbf{7} clairs. Il y en a donc \textbf{1 de plus} du côté des clairs.}\par\addvspace{0.4em}
\noindent \textbf{2.}\par\addvspace{0.35em}
\noindent{\color{green!45!black}\textbf{Le raisonnement clé.} Chaque rue relie un carrefour sombre à un carrefour clair. Donc à chaque fois que le car roule, il \textbf{change de couleur} : ses arrêts sont sombre, clair, sombre, clair\dots{} \textbf{en alternance}.}\par\addvspace{0.4em}
\noindent{\color{red!80!black}\bfseries Une tournée qui dessert les 13 carrefours alterne donc les deux couleurs d'un bout à l'autre : elle en utilise \textbf{autant de chaque, à un près}. Et si elle en utilise un de plus d'une couleur, c'est forcément celle de son \textbf{départ} et de son \textbf{arrivée}.}\par\addvspace{0.4em}
\noindent \textbf{3.}\par\addvspace{0.35em}
\noindent{\color{red!80!black}\bfseries \textbf{Non.} Un circuit revient à son point de départ : il compte autant d'arrêts sombres que de clairs. Or ce quartier a 6 carrefours sombres et 7 clairs — c'est impossible.}\par\addvspace{0.4em}
\noindent \textbf{4.}\par\addvspace{0.35em}
\noindent{\color{red!80!black}\bfseries \textbf{Non plus.} Avec un carrefour clair de plus, la tournée doit \textbf{partir et arriver} sur un carrefour clair. Or l'école est en \textbf{M}, qui est sombre.}\par\addvspace{0.4em}
\noindent{\color{green!45!black}Une tournée existe pourtant dans ce quartier : il suffirait d'installer l'école sur un carrefour clair. Ce n'est pas le plan qui est en cause, c'est l'endroit d'où l'on part.}\par\addvspace{0.4em}
\end{document}
