HMMT 二月 2000 · GEN 赛 · 第 16 题
HMMT February 2000 — GEN Round — Problem 16
题目详情
英文原题
- Jo e bik es x miles East at 20 mph to his friend's house. He then turns South and bik esx miles at 20 mph to the store. Then, Jo e turns East again and go es to his grandma'shouse at 14 mph. On this last leg, he has to arry our he b ough t for her at the store.
Her house is 2 more miles from the store than Jo e's friend's house is from the store.
Jo e sp ends a total of 1 hour on the bik e to get to his grandma's house. If Jo e then ridesstraigh t home in his grandma's heli opter at 78 mph, ho w man y min utes do es it tak e
Jo e to get home from his grandma's house?
解析
英文解析
- Expressing the total time Jo e has bik ed in hours leads to the equation + + = 1.
20 20 14
So, x = 5. Th us, we an onstru t the diagram b elo w, and nd the total time that it
1 1
tak es to get ba k: 13 = hours, or 10 min utes .
78 6
5 mi. Friend’s house
5 mi.
13 mi.
Gma’s houseshore 7 mi.
12 mi.