There are six period every day in a school on 5 subjects are to be taught in a day.In how many ways can the subjects be taught in a days?

In how many ways can one post 3 letters in 5 post boxes?

There are 7 boys and 3 girls in a class. In how many ways can they be arranged in a row such that no two girls are together?

A factory requires 42 machines to produce a given number of articles in 63 days. How many machines would be required to produce the same number of articles in 54 days?

If earth be at half of its present distance from the sun, how many days will there be in a year?

From 10 boys and 20 girls, a committee of 2 boys and 3 girls is to be formed. In how many ways can this be done if a particular boy is included

Indian cricket team consists of 6 bowlers and 8 batsmen from which playing eleven is to be selected including atleast 4 bowlers. In how many ways can this be done?

If the radius of earth becomes half of it's present radius how many times decrease in a day.

In how many different ways can one invite 3 or more of his 6 friends?

From 10 boys and 20 girls, a committee of 2 boys and 3 girls is to be formed. In how many ways can this be done if a particular girl is included

From 10 boys and 20 girls, a committee of 2 boys and 3 girls is to be formed. In how many ways can this be done if a particular girl is excluded.