Two large and 1 small pumps can fill a swimming pool in 4 hours. One large and 3 small pumps can also fill the same swimming pool in 4 hours. How many hours will it take 4 large and 4 small pumps to fill the swimming pool. (We assume that all large pumps are similar and all small pumps are also similar.)
+36914 1/(2L+s) =4 and
1/(L+3s)=4 equating the denominators leads to L = 2s subbing into one of the equations finds
s = 1/20 so L = 2/20
now for FOUR of them
1 /( 4(2/20) + 4 (1/20) ) = 1/ (12/20) = 20 /12 = 1 2/3 hr for 4 of each pump to fill the pool
