比例

LeannaChina

Q2:
In planning for a trip, Joan estimated both the distance of the trip, in miles, and her average speed, in miles per hour.She accurately divided her estimated distance by her estimated average speed to obtain an estimate for the time, in hours, that the trip would take.Was her estimate within 0.5 hour of the actual time that the trip took?
(1)Joan’s estimate for the distance was within 5 miles of the actual distance.
(2) Joan’s estimate for her average speed was within 10 miles per hour of her actual average speed.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

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sdcar2010

If the error of her estimation is 0, the answer to the question of 0.5 hour is yes.

But let's take a look at the other extreme. Her distance finished was 100 miles. Her estimate was 105 miles. Her actual speed was 15 mph. But her estimate was 5 mph. Then what is the difference between the actual time and the calculated estimate time?

erijing

我选E

arthur06

我是這麼理解的
V=9.5~10.4
D=4.9~5.4
so, T有可能為0.5 or 0.6(if D=4.9, V=9.5 ,t約0.56四捨五入為0.6)
所以為E no sufficient