Q13:c／ｅ

Is the number of seconds required to travel d1 feet at r1 feet per second greater than the number of seconds required to travel d2 feet at r2 feet per second?

(1) d1 is 30 greater than d2.

(2) r1 is 30 greater than r2.

I think C is right. Is d1/r1 greater than

d2/r2?

d1/r1-d2/r2=(d1*r2-d2*r1)/(r1*r2)

if together with term 1 and 2,

d1=1.3d2 and r1=1.3r2 ,

so (d1*r2-d2*r1)/(r1*r2)=(1.3d2*r2-d2*1.3r2)/(r1*r2)=0

therefore, the time is the same.

in other words, it suffiently answer the question.

Am I right?

30greater不是30%greater

如下图，当d2=r2的时候，t=1秒，两个时间相等

当d2/r2<1的时候，t<1秒，t1>t2，2快

当d2/r2>1的时候，t>1秒，t2>t1 1块

so E