Average Speed Question

[hijazim]

Clearly the answer should be = 70miles/2h = 35 miles/h
So the nearest is 35.5 which is answer D.
The right answer in the book is 34.3 which is C

Any suggestions why??

[deepoe]

Assume he drove 30 miles in 1 hour ( 30 m/h )

Than he drove the 30 miles with a speed of 40 m/h.

30 / 40 = 0,75 H

1,75 H he took for both drives.


60 / 1,75 = 34,3

[hijazim]

Thx man.. It's really not that hard.. but the approach is the thing.. thx again

[deepoe]

Thx man.. It's really not that hard.. but the approach is the thing.. thx again

Jep I got that problem too with some of the GMAT questions hehe

[bhavikrao]

folks,

If you the same distance but different speeds, the formula is

2ab/a+b

= 2*30*40/30+40

and you will get the answer

[krisraam]

Assume he drove 30 miles in 1 hour ( 30 m/h )

Than he drove the 30 miles with a speed of 40 m/h.

30 / 40 = 0,75 H

1,75 H he took for both drives.


60 / 1,75 = 34,3

When assuming values assume the values in such a way that we don't run into decimals.

Usually the LCM of the values

Here 30 and 40 are the numbers.

Assume he traveled 120 miles instead of 30.

Thanks
raama