Rajeed, Debangana, Masuum and Tajmira can do 150 sums in 6 days. If each of them does equal number of sums everyday in how many days will Rajeeb and Tajmira finish 250 sums?

8 men can do a piece of work in 15 days. Find in how many days will 10 men finish the same work.

2 men and 6 boys together can do a piece of work in 5 days . 8 men and 3 boys together can do the same work in 3 days . In how many days 1 man and 3 boys together can do the same work ?

How many even numbers are there between 91 and 259 ? Find also the sum of the even numbers between them.

In how many ways can four people, each throwing a dice once, make a sum of 6?

In how many ways can three persons, each throwing a single dice once, make a sum of 15?

Six cards are drawn one by one from a set of unlimited number of cards, each card is marked with numbers -1, 0 or 1 . Number of different ways in which they can be drawn if the sum of the numbers shown by them vanishes is

Three balls marked with 1, 2 and 3 are placed in an urn. One ball is drawn, its number is noted, then the ball is returned to the urn. This process is repeated and then repeated once more. Each ball is equally likely to be drawn on each occasion. If the sum of the number noted is 6, then the probability that the ball numbered with 2 is drawn at all the three occassion, is

6 persons can complete a work in 7 days. Let's find how many persons will be required to finish the work in 21 days. In matheatical language, the problem may be stated as