Bunuel wrote:
It takes Avery 3 hours to build a brick wall while Tom can do it in 2.5 hours. If the two start working together and after an hour Avery leaves, how much time will it take Tom to complete the wall on his own?
A. 25 minutes.
B. 30 minutes.
C. 40 minutes.
D. 55 minutes.
E. 1 hour and 20 minutes.
Avery’s rate is ⅓ and Tom’s rate is 1/(2.5) = 2/5 . We can let Avery’s time = 1 hour and Tom’s time = 1 + x hours; thus:
(1/3)(1) + (1/2.5)(1 + x) = 1
1/3 + (2/5)(1 + x) = 1
Multiplying by
...