Bunuel wrote:

If during a one-day period the Q train arrives at the station 30% less frequently than the B train, and the B train arrives 10% less frequently than the F train, then the Q train`s frequency is what percent of the F train`s frequency?

A. 27

B. 40

C. 60

D. 63

E. 90

We can create the equations:

Q = 0.7B

And

B = 0.9F

Substitute the second equation into the first, we have:

Q = 0.7(0.9F)

Q = 0.63F

Thus, the Q train’s frequency is 63 percent of the F train’s frequency.

Alternate Solution:

Let’s assume that the F train has 100 arrivals daily. The B train would then have (100)(0.9) = 90 arrivals, and the Q train would have (90)(0.7) = 63 arrivals. Thus, the Q train would have 63/100, or 63%, of the number of arrivals of the F train.

Answer: D

_________________

Scott Woodbury-Stewart

Founder and CEO

GMAT Quant Self-Study Course

500+ lessons 3000+ practice problems 800+ HD solutions