Car A and Car B

From the area, you can get radius and from that you can get Circumference "C"
This question now boils down to cars A and B which are "C"miles apart, traveling towards each other at speeds of X and Y respectively. How long will they take to meet??

Approx 75mins?

Unless I missed some way to simplify the math, this problem isn't very GMATy. First need to take sqrt(1256/pi) to get the radius. You can guesstimate to around 20. Then need the circumference which involves multiplying by pi and then dividing the distance by the rate. I get 75 as well, but again, I don't see how to avoid doing calculations using a numerical estimation of pi

Radius = sqrt(A/pi) = sqrt(1256/3.14) =sqrt(400) = 20

Circumference = 40*pi = 125.6

Car A is going to have to travel 40% of the way round and car B 60% of the way.

Car A travels: 40% of 125.6 = 12.56 x 4 = 50.24 miles

Time = D/S = 50.24/40 = 1.256 hours = 75mins (approx)

cm47323 wrote:Unless I missed some way to simplify the math, this problem isn't very GMATy. First need to take sqrt(1256/pi) to get the radius. You can guesstimate to around 20. Then need the circumference which involves multiplying by pi and then dividing the distance by the rate. I get 75 as well, but again, I don't see how to avoid doing calculations using a numerical estimation of pi

I think that's what makes the difference in the real exam. A tough question will be tedious to answer (not necessarily always) & someone who is very good (caliber of above 720) will quickly do a comfortable approximation & arrive at the answer, while someone like me would sit calculating each component, spend a lot of energy & get bogged down by the ticking time :roll:

I share your thoughts Vamuri!

This question is from 800score.com . While their questions park is good, the questions are not very gmat-like. I'vefound many hard questions in gmatprep and gmatfocus, but they simply aren't this difficult or "weird"

This question is not at all GMAT like, as has already been noted.

When the direction of a moving body changes it cannot have uniform speed. Constantly varying speeds involve a concept called accelaration, which the GMAT DOES NOT COVER.

Can this be done, assuming speed is a scalar quantity...sure...but it's not very accurate.

One can use relative speed to cut down further on calculations here.

R= sqrt(A/pi) = sqrt(1256/3.14) =sqrt(400) = 20

Time taken(in min.) = (Total Distance / Total relative speed ) *60
= ((2*3.14*20)/100)* 60 = 75 (approx)

Relative speed will be the sum of A & B as they are moving towards each other.

Cheers

anshulseth wrote:One can use relative speed to cut down further on calculations here.

R= sqrt(A/pi) = sqrt(1256/3.14) =sqrt(400) = 20

Time taken(in min.) = (Total Distance / Total relative speed ) *60
= ((2*3.14*20)/100)* 60 = 75 (approx)

Relative speed will be the sum of A & B as they are moving in the same dir.

Cheers

I am positive it was a typo anshuleth.

If using Relative Speeds:
a) Bodies moving in Same direction (Subtract speeds for resultant effective speed)
b) Bodies moving in Opposite direction (Add speeds for resultant effective speed)

@Musiq
I am right and u are also right.
Now, how do u explain that.

I meant relative speed adds when objects move towards each other,
and u say that they add when they move in opposite direction.
Which is one and the same here, clockwise and anti-clockwise..

Got it.. :roll:

Though i must correct my post to say, that they are moving towards each other.