Two pipes A and B can fill a tank in 15 h and 18 h respectively. Both pipes are opened simultaneously to fill the tank. In how many hours will the empty tank be filled?

Two persons A and B appear in an interview for two vacancies. If the probabilities of their selections are 1/4 and 1/6 respectively, then the probability that none of them is selected is

The diagonal of a rectangle is 15 cm and its length is 12 cm. Find the area of the rectangle.

Sunita invested ₹12000 on simple interest at the rate of 10% per annum to obtain a total amount of ₹20400 after a certain period. For how many years did she invest to obtain the above amount?

Richa travels from A to B at a speed of 15 km/h, from B to C at 20 km/h and from C to D at 30 km/h. If AB = BC = CD, find Richa's average speed.

The HCF and LCM of two numbers m and n are 6 and 210 respectively. If m + n = 72, then 1/m + 1/n is equal to

(1 - 1/3)(1 - 1/4)(1 - 1/5)...(1 - 1/25) is equal to

The average salary per head of all workers of an institution is 60. The average salary per head of 12 officers is 400. The average salary per head of the rest is 56. Then the total number of workers in the institution is

Evaluate √(0.289/0.00121) + √(64/16)