In a car race between A and B over a distance of 60 miles

Question

In a car race between A and B over a distance of 60 miles, B gives an hour lead to A. If A finishes the race in 4 hour assuming both A and B travel at constant speed, how much time does B take?
(1) B crosses A in exactly one hour.
(2) B finishes the race one hour before A.

Self Made

Kurtosis · Answer

Given: B gives an hour lead to A. 
A finishes in 4 hours
Distance = 60 miles

St1: B crosses A in 1 hour --> When B crosses A, time taken by A = 2hrs; time taken by B = 1hr
Hence, Speed of B is double the speed of A
If A takes 4 hours, B takes 2 hours to complete. 
Sufficient

St2: Time taken by A = 4
B leaves 1 hour after A and completes 1 hour before A --> Time taken by B = 2 hours. 
Sufficient

Answer: D

stonecold · Answer

Nice and tricky
Here let speed of car B be x mph
now speed of car A = 15mph
we need to get x as then we can use time = 60/x
from 1 => x = 30 => time = 60/30 => 2 hours.
hence sufficient.
from 2 => time = 3hours total => 3-1 (for the lead) hence 2 hours 
.so D is my choice

Part two here is excellent. i bet if it were a PS question for part two how many of us would solve that

regards
StoneCold

ronny123 · Answer

Distance= 60 miles
B gives A a headstart of 1 hour
A takes 4 hours

Statement 1 :B crosses A in exactly one hour.

Which means that the distance traveled by A in 2 hours is covered by B in an hour
So if time taken by A is 4 hours, B takes 2

Sufficient

Statement 2 : B finishes the race one hour before A

A takes 4 hours to finish
B completes the race an hour before and also starts an hour later
So, B takes 2 hours to complete

Sufficient

Correct option : D

Youraisemeup · Answer

D is my choice too. Explanation same as other fellow members.

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In a car race between A and B over a distance of 60 miles

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GMAT Data Sufficiency (DS) Questions

In a car race between A and B over a distance of 60 miles

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