GMAT Quantitative Reasoning Practice Test 3

Question : 16 of 100

Marks: +1, -0

Three cars are starting to drive from three corners of a huge axi-cimetrical triangle towards the middle. Car A can travel at a speed of 110 miles per hour, car B can travel 10% less and car C can travel the average speed of the first two cars.
If all cars leave at the same time and it took car A 30 minutes to get to the middle, how long approximately after car C reached the middle, did car B reached it?

About 15 minutes.
About 10 minutes.
About 5 minutes.
About 1.5 minutes.
They reached the middle at the same time.

Validate

Solution:

Start with the speeds of the cars:
Car A can travel at

110 {\mp}{/} {\h}

.
Car B can travel at a speed of

(110 × 0.9) 99 {\mp} {/} {\h}

.
Car C can travel at a speed of

(110+99) \/ 2=104.5 {\mp} {/} {\h}

.
If it took car A 30 minutes, the length towards the middle of the triangle is 55 miles.
Calculate how long it takes car B and car C travel 55 miles:
Car B: It will take her (55/99) hours which is 33 minutes and a third.
Car C: It will take her

(55 {/}104.5)

hours which is approximately 31.6 minutes.
Therefore, the differences in the time will be approximately 1.5 minutes.

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