新SAT官方Daily Practise每日一题数学代数题

小站教育2017-06-16 09:59:35

10461
问题相似?试试立即获取解答吧~
摘要:今天起,本系列将给大家带来SAT官方的每日一练真题,各个项目都有,持续更新,希望大家同步多练习。今天这里分享的是6月15日的数学代数题,一起来练习吧!


答案:B

解析:

Choice B is correct. Let t represent the time, in seconds, that Sam spends running, let d represent the distance run, and let r represent the rate at which Sam is moving.

Then, since d=rt, 5t represents the total distance, in meters, Sam runs in t seconds.

Since Lisa gives her little brother a 15-second head start, it follows that she runs for t-15 seconds at a rate of 8 m/sec.

So, 8(t-15) represents the total distance, in meters, Lisa runs in(t-15) seconds.

If Lisa catches Sam, they would have covered the same distance. Therefore, we can set up the following equation and solve for t:

8(t-15)=5t

8t-120=5t

3t=120

t=40

Since t represent the time, in seconds, that Sam spends running, this shows that Sam will run for 40 seconds before his sister catches him.

Since Lisa runs for t-15 seconds, it follows that she runs for 25 seconds before catching up with Sam.

下载小站SAT APP,刷SAT真题

本文来自于小站教育【SAT数学】专栏,转载请以超链接形式标注本文出处,并附上此申明,否则将追究法律责任。

看完仍有疑问?想要更详细解答?

相关推荐