Difference between revisions of "2023 AMC 8 Problems/Problem 13"

Latest revision as of 22:21, 21 January 2024

Problem

Along the route of a bicycle race, $7$ water stations are evenly spaced between the start and finish lines, as shown in the figure below. There are also $2$ repair stations evenly spaced between the start and finish lines. The $3$ rd water station is located $2$ miles after the $1$ st repair station. How long is the race in miles? $[asy] // Credits given to Themathguyd‎ and Kante314 usepackage("mathptmx"); size(10cm); filldraw((11,4.5)--(171,4.5)--(171,17.5)--(11,17.5)--cycle,mediumgray*0.4 + lightgray*0.6); draw((11,11)--(171,11),linetype("2 2")+white+linewidth(1.2)); draw((0,0)--(11,0)--(11,22)--(0,22)--cycle); draw((171,0)--(182,0)--(182,22)--(171,22)--cycle); draw((31,4.5)--(31,0)); draw((51,4.5)--(51,0)); draw((151,4.5)--(151,0)); label(scale(.85)*rotate(45)*"Water 1", (23,-13.5)); label(scale(.85)*rotate(45)*"Water 2", (43,-13.5)); label(scale(.85)*rotate(45)*"Water 7", (143,-13.5)); filldraw(circle((103,-13.5),.2)); filldraw(circle((98,-13.5),.2)); filldraw(circle((93,-13.5),.2)); filldraw(circle((88,-13.5),.2)); filldraw(circle((83,-13.5),.2)); label(scale(.85)*rotate(90)*"Start", (5.5,11)); label(scale(.85)*rotate(270)*"Finish", (176.5,11)); [/asy]$ $\textbf{(A)}\ 8 \qquad \textbf{(B)}\ 16 \qquad \textbf{(C)}\ 24 \qquad \textbf{(D)}\ 48 \qquad \textbf{(E)}\ 96$

Solution

Suppose that the race is $d$ miles long. The water stations are located at $\frac{d}{8}, \frac{2d}{8}, \ldots, \frac{7d}{8}$ miles from the start, and the repair stations are located at $\frac{d}{3}, \frac{2d}{3}$ miles from the start.

We are given that $\frac{3d}{8}=\frac{d}{3}+2,$ from which $\begin{align*} \frac{9d}{24}&=\frac{8d}{24}+2 \\ \frac{d}{24}&=2 \\ d&=\boxed{\textbf{(D)}\ 48}. \end{align*}$ ~apex304, SohumUttamchandani, wuwang2002, TaeKim, Cxrupptedpat, MRENTHUSIASM

Video Solution by Math-X (Let's first Understand the question)

https://youtu.be/Ku_c1YHnLt0?si=YRjrl2U0waLkNWqm&t=2151 ~MATH-X

Video Solution (CREATIVE THINKING!!!)

https://youtu.be/rPRis7sGroI

~Education, the Study of Everything

Video Solution (Animated)

https://youtu.be/NivfOThj1No

~Star League (https://starleague.us)

Video Solution by Magic Square

https://youtu.be/-N46BeEKaCQ?t=4439

Video Solution by Interstigation

https://youtu.be/DBqko2xATxs&t=1299

Video Solution by harungurcan

https://www.youtube.com/watch?v=VqN7c5U5o98&t=16s

~harungurcan

@@ Line 1: / Line 1: @@
-⠀⠀⠀⠀⠀⠀⠀⠀⠀⣠⣴⣶⣿⣿⣷⣶⣄⣀⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀
+==Problem==
-⠀⠀⠀⠀⠀⠀⠀⠀⠀⣰⣾⣿⣿⡿⢿⣿⣿⣿⣿⣿⣿⣿⣷⣦⡀⠀⠀⠀⠀⠀
-⠀⠀⠀⠀⠀⠀⠀⢀⣾⣿⣿⡟⠁⣰⣿⣿⣿⡿⠿⠻⠿⣿⣿⣿⣿⣧⠀⠀⠀⠀
+Along the route of a bicycle race, <math>7</math> water stations are evenly spaced between the start and finish lines,
-⠀⠀⠀⠀⠀⠀⠀⣾⣿⣿⠏⠀⣴⣿⣿⣿⠉⠀⠀⠀⠀⠀⠈⢻⣿⣿⣇⠀⠀⠀
+as shown in the figure below. There are also <math>2</math> repair stations evenly spaced between the start and
-⠀⠀⠀⠀⢀⣠⣼⣿⣿⡏⠀⢠⣿⣿⣿⠇⠀⠀⠀⠀⠀⠀⠀⠈⣿⣿⣿⡀⠀⠀
+finish lines. The <math>3</math>rd water station is located <math>2</math> miles after the <math>1</math>st repair station. How long is the race
-⠀⠀⠀⣰⣿⣿⣿⣿⣿⡇⠀⢸⣿⣿⣿⡀⠀⠀⠀⠀⠀⠀⠀⠀⣿⣿⣿⡇⠀⠀
+in miles?
-⠀⠀⢰⣿⣿⡿⣿⣿⣿⡇⠀⠘⣿⣿⣿⣧⠀⠀⠀⠀⠀⠀⢀⣸⣿⣿⣿⠁⠀⠀
+<asy>
-⠀⠀⣿⣿⣿⠁⣿⣿⣿⡇⠀⠀⠻⣿⣿⣿⣷⣶⣶⣶⣶⣶⣿⣿⣿⣿⠃⠀⠀⠀
+// Credits given to Themathguyd‎ and Kante314
-⠀⢰⣿⣿⡇⠀⣿⣿⣿⠀⠀⠀⠀⠈⠻⣿⣿⣿⣿⣿⣿⣿⣿⣿⠟⠁⠀⠀⠀⠀
+usepackage("mathptmx");
-⠀⢸⣿⣿⡇⠀⣿⣿⣿⠀⠀⠀⠀⠀⠀⠀⠉⠛⠛⠛⠉⢉⣿⣿⠀⠀⠀⠀⠀⠀
+size(10cm);
-⠀⢸⣿⣿⣇⠀⣿⣿⣿⠀⠀⠀⠀⠀⢀⣤⣤⣤⡀⠀⠀⢸⣿⣿⣿⣷⣦⠀⠀⠀
+filldraw((11,4.5)--(171,4.5)--(171,17.5)--(11,17.5)--cycle,mediumgray*0.4 + lightgray*0.6);
-⠀⠀⢻⣿⣿⣶⣿⣿⣿⠀⠀⠀⠀⠀⠈⠻⣿⣿⣿⣦⡀⠀⠉⠉⠻⣿⣿⡇⠀⠀
+draw((11,11)--(171,11),linetype("2 2")+white+linewidth(1.2));
-⠀⠀⠀⠛⠿⣿⣿⣿⣿⣷⣤⡀⠀⠀⠀⠀⠈⠹⣿⣿⣇⣀⠀⣠⣾⣿⣿⡇⠀⠀
+draw((0,0)--(11,0)--(11,22)--(0,22)--cycle);
-⠀⠀⠀⠀⠀⠀⠀⠹⣿⣿⣿⣿⣦⣤⣤⣤⣤⣾⣿⣿⣿⣿⣿⣿⣿⣿⡟⠀⠀⠀
+draw((171,0)--(182,0)--(182,22)--(171,22)--cycle);
-⠀⠀⠀⠀⠀⠀⠀⠀⠀⠉⠻⢿⣿⣿⣿⣿⣿⣿⠿⠋⠉⠛⠋⠉⠉⠁⠀⠀⠀⠀
-⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠈⠉⠉⠉⠁
+draw((31,4.5)--(31,0));
+draw((51,4.5)--(51,0));
+draw((151,4.5)--(151,0));
+label(scale(.85)*rotate(45)*"Water 1", (23,-13.5));
+label(scale(.85)*rotate(45)*"Water 2", (43,-13.5));
+label(scale(.85)*rotate(45)*"Water 7", (143,-13.5));
+filldraw(circle((103,-13.5),.2));
+filldraw(circle((98,-13.5),.2));
+filldraw(circle((93,-13.5),.2));
+filldraw(circle((88,-13.5),.2));
+filldraw(circle((83,-13.5),.2));
+label(scale(.85)*rotate(90)*"Start", (5.5,11));
+label(scale(.85)*rotate(270)*"Finish", (176.5,11));
+</asy>
+<math>\textbf{(A)}\ 8 \qquad \textbf{(B)}\ 16 \qquad \textbf{(C)}\ 24 \qquad \textbf{(D)}\ 48 \qquad \textbf{(E)}\ 96</math>
+==Solution==
+Suppose that the race is <math>d</math> miles long. The water stations are located at <cmath>\frac{d}{8}, \frac{2d}{8}, \ldots, \frac{7d}{8}</cmath> miles from the start, and the repair stations are located at <cmath>\frac{d}{3}, \frac{2d}{3}</cmath> miles from the start.
+We are given that <math>\frac{3d}{8}=\frac{d}{3}+2,</math> from which
+<cmath>\begin{align*}
+\frac{9d}{24}&=\frac{8d}{24}+2 \\
+\frac{d}{24}&=2 \\
+d&=\boxed{\textbf{(D)}\ 48}.
+\end{align*}</cmath>
+~apex304, SohumUttamchandani, wuwang2002, TaeKim, Cxrupptedpat, MRENTHUSIASM
+==Video Solution by Math-X (Let's first Understand the question)==
+https://youtu.be/Ku_c1YHnLt0?si=YRjrl2U0waLkNWqm&t=2151  ~MATH-X
+==Video Solution (CREATIVE THINKING!!!)==
+https://youtu.be/rPRis7sGroI
+~Education, the Study of Everything
+==Video Solution (Animated)==
+https://youtu.be/NivfOThj1No
+~Star League (https://starleague.us)
+==Video Solution by Magic Square==
+https://youtu.be/-N46BeEKaCQ?t=4439
+==Video Solution by Interstigation==
+https://youtu.be/DBqko2xATxs&t=1299
+==Video Solution by harungurcan==
+https://www.youtube.com/watch?v=VqN7c5U5o98&t=16s
+~harungurcan
+==See Also==
+{{AMC8 box|year=2023|num-b=12|num-a=14}}
+{{MAA Notice}}

2023 AMC 8 (Problems • Answer Key • Resources)
Preceded by Problem 12	Followed by Problem 14
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25
All AJHSME/AMC 8 Problems and Solutions

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