A set (X) of 20 pipes can fill 70% of a tank in 14 minutes. Another set (Y) of 10 pipes fills 3/8th of the tank in 6 minutes. A third set (Z) of 16 pipes can empty half of the tank in 20 minutes. If half of the pipes of set X are closed and only half of the pipes of set Y are open, and all pipes of the set (Z) are open, then how long will it take to fill 50% of the tank?

X can complete one-third of a certain work in 6 days, Y can complete one-third of the same work in 8 days and Z can complete three-fourth of the same work in 12 days. All of them work together for n d…

A natural number N is such that it can be expressed as N = p + q + r , where p, q and r are distinct factors of N. How many numbers below 50 have this property?

Three prime numbers p, q and r, each less than 20, are such that p - q = q - r . How many distinct possible values can we get for (p + q + r) ?

How many possible values of (p + q + r) are there satisfying (1)/(p) + (1)/(q) + (1)/(r) = 1 , where p, q and r are natural numbers (not necessarily distinct)?

Team X scored a total of N runs in 20 overs. Team Y tied the score in 10% less overs. Had team Y's average run rate (runs per over) been 50% higher, the scores would have been tied in 12 overs. How ma…

The price (p) of a commodity is first increased by k% ; then decreased by k% ; again increased by k% ; and again decreased by k% . If the new price is q , then what is the relation between p and q ?