Machines P and Q are two different machines that make items in a factory. When Machine P works alone, it covers 15 items in m hours. When Machines P and Q work simultaneously at their respective rates, they cover 15 items in n hours. In terms of m and n, how many hours does it take Machine Q, working alone at its constant rate, to cover 15item?
Select the correct option
A) m
B) n
C) 15n/225-mn
D) m+n
E) m-n
working rate p = 15/m ; working rate pq =( 1/p +1/q)* n =15 or mn/15 +n/q =15 0r n/q = 15-mn/15 = 225-mn/15   q = 15n/225-mn   15n/225-mn
<result>C</result>
Machines P and Q are two different machines that make items in a factory. When Machine P works alone, it covers 15 items in m hours. When Machines P and Q work simultaneously at their respective rates, they cover 15 items in n hours. In terms of m and n, how many hours does it take Machine Q, working alone at its constant rate, to cover 15item?