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# The time it took car P to travel 600 miles was 2 hours less than the

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Re: The time it took car P to travel 600 miles was 2 hours less than the [#permalink]
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Rather than going for assuming speed to be 'x', try doing by hit n trial.

1st chance: (Assume)Time taken by R = 12 hours

Distance: 600 miles.

Speed: 50 miles per hour.

Therfore, Time taken by P = 12 - 2 = 10 hours
Distance: 600 miles.

Speed: 60 miles per hour.

Car P’s average speed was 10 miles per hour greater than that of car R - Proved.

2nd chance: Try with options.

Suppose we pick option D.
But try taking the option that divides 600 completely. So, try taking 60.

R = 60 miles per hour - Distance = 600 - Time taken = 10 hour.
P = 60+10 = 70 miles per hour - Distance = 600 - Time taken = 9.x hour (not 2 hours less than R).

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Re: The time it took car P to travel 600 miles was 2 hours less than the [#permalink]
I tried with options
I usually start picking B out. I know that:

R: Avg: y Time: x Distance: 600
P: Avg: y+10 Time: x-2 Distance: 600
If i try with answer B, i get:
R: Avg: 50 Time: 12 Distance: 600
P: Avg: 60 Time: 10 Distance: 600
YES!

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The time it took car P to travel 600 miles was 2 hours less than the [#permalink]
Bunuel wrote:
The time it took car P to travel 600 miles was 2 hours less than the time it took car R to travel the same distance. If car P’s average speed was 10 miles per hour greater than that of car R, what was car R’s average speed, in miles per hour?

A. 40
B. 50
C. 60
D. 70
E. 80

I always get confused with these types of problems. So here's another approach. It's a little lengthy but easy!
Since, the numbers are very simple, the calculations should not take a lot of time!
Let's use the options:
A: If Speed of R= 40 mph
then time taken will be, t=d/s
t= 600/40= 15 hours

Now, we know, that P(t)= t-2= 13
And P(s)= s+10= 50 mph
D= s*t and we know D=600 miles
So, now, D= 13*50= 650 miles

B: R=50 mph
t= 600/50= 12hours
Now, P(t)= 10 hours
S= 60 mph
D= 60*10= 600 miles
CORRECT

Hence, Speed for R should be 50 mph
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Re: The time it took car P to travel 600 miles was 2 hours less than the [#permalink]
Bunuel wrote:
The time it took car P to travel 600 miles was 2 hours less than the time it took car R to travel the same distance. If car P’s average speed was 10 miles per hour greater than that of car R, what was car R’s average speed, in miles per hour?

A. 40
B. 50
C. 60
D. 70
E. 80

Solution:

Since the answer choices are easy numbers, let’s solve the problem numerically instead of algebraically. That is, we can check each answer choice until we find the correct answer.

If car R’s speed is 40 mph, then car P’s speed is 50 mph. Furthermore, it will take car R 600/40 = 15 hours and car P 600/50 = 12 hours to travel 600 miles. However, since 12 is not 2 less than 15, we see that choice A is not the correct answer.

If car R’s speed is 50 mph, then car P’s speed is 60 mph. Furthermore, it will take car R 600/50 = 12 hours and car P 600/60 = 10 hours to travel 600 miles. However, since 10 is 2 less than 12, we see that choice B is the correct answer.

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Re: The time it took car P to travel 600 miles was 2 hours less than the [#permalink]
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Re: The time it took car P to travel 600 miles was 2 hours less than the [#permalink]
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