The average weight of five persons sitting in a boat is 38 kg. The average weight of the boat and the persons sitting in the boat is 52kg. What is the weight of the boat?

If $$ ({x+y\over z})=2$$ , then what is the value of $$ [{ {y\over {y-z}}}] +[{ {x\over {x-z}}}]$$.

$$ {{2^n+2^{n-1}}\over {2^{n+1} -2^n}}=?$$

Running at the speed of 3 km/hr., a person reaches his destination 10 minutes later than usual time. if he increases his speed by 1 km/hr., he reaches his destination 15 min earlier. and the distance to his destination.

If A’s income is 40 % less than that of B, how much percent B's income is more than that of A? 

There are 10 balls, some of them are red and the others white. The average cost of all the balls is Rs. 28, average cost of red balls Rs. 25 and that of white balls is Rs. 30, the number of white balls is: 

Given that ( 1² +2²+3²+………..+10²)=385, the value of (2²+4²+6²+……20²) is equal to

The sum of all interior angles of a regular polygon is twice the sum of all its exterior angles.  The number of sides of the polygon is