A tap can fill a tank in 6 hours. After half the tank is filled, three more similar taps are opened. What is the total time taken to fill the tank completely?

If (2^x)(2^y) = 8 and (9^x)(3^y) = 81 , then ( x , y ) is : 

The volume of a sphere and an elliptical cylinder are the same. The radius of the sphere and cylinder are 21 cm and 14 cm respectively. What is the height of the cylinder?

28% members of a certain group are married. What is the respective ratio between the number of married members to the number of unmarried members?

On dividing a certain number by 342 we get 47 as remainder. If the same number is divided by 18, what will be the remainder?

If x²+y²+z² = xy + yz + zx, then the value of $${3x^4+7y^4+5z^4}\over{5x^2y^2+7y^2z^2+3z^2x^2} $$ is

The sum of two numbers is 232 and their HCF is 29. What is the numbers of such pairs of numbers satisfied the above condition?

If 2x + 3y = 87 and 3x – 3y = 48, what is the value of x?