RM wrote:A certain business printer can print 40 characters per second, which is 4 times as fast as an average printer. If an average printer can print 5 times as fast as an electric typewriter, how many characters per minute can an electric typewriter print?
(A) 2
(B) 32
(C) 50
(D) 120
(E) 600

Sol'n: 120

b = business printer
a = average printer
e = electric typewriter

b = 4a : business printer is 4 times faster than average printer.
a = 5e : average printer is 5 times faster than the electric typewriter.

so we have ratios for solve for all three. We are given that b prints 40 per second, so...

if b is 40, then a = 10,
then if a = 10, then e = 2

so electric typewriter prints 2 characters per second,
so then it prints 2 * 60 = 120 characters per minute -> choice D.

Yep