Time taken by Helen to reach her house =?
Statement I
Helen's average speed = 72 mph
We dont know anything about the distance .
Insufficient
Statement II
If the avg. speed is 8 more the time taken is 1 hr less
We dont know anything about the distance
Insufficient.
Combining I & II
72*t = d
(72+9)*(t-1) = d, I am taking 9, greater than 8
81*(t-1) = 72*t
81t - 81 = 72t
9t = 81
t=9
Hence Sufficient.
Hence C.
Whats the OA?
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Source: Beat The GMAT — Data Sufficiency |
I agree with C
But I think that (72+9)*(t-1) = d
Should be (72+8)*(t-1) = d
solving 72t=80(t-1)
t=10
Why you decided to add 9?
Question states the "if the speed was 8 kmph greater"
But I think that (72+9)*(t-1) = d
Should be (72+8)*(t-1) = d
solving 72t=80(t-1)
t=10
Why you decided to add 9?
Question states the "if the speed was 8 kmph greater"
