In a row of boys, if A is 10th from left and B is 9th from the right and interchange their positions, A becomes 15th from the left. How many boys are there in the row?

In a certain code SISTER is written as RHRSDQ. How is UNCLE written in that code? 

Assertion (A): James Watt invented the steam engine.
Reason (R): It was invented to pump out the water from the flooded mines.

380, 645, 557, 656, 762, 875, ?

Three of the following four words are alike in a certain way and one is different. Pick the odd word out.

Direction: In the following question, select the related letters from the given alternatives.
Food : Hunger :: Sleep : ? 

In the given figure, how many metallic balls are also heavy?

In the following diagram find the missing number?