How many four-digit natural numbers are there such that all of the digits are even ?

Four digit numbers are formed by using the digits 1, 2, 3, 5 without repetition of digits. How many of them are divisible by 4?

What is the sum of all four digit numbers formed by using all digits 0, 1, 4, 5 without repetition of digits ?

How many 3-digit numbers can be formed from the digits 2, 3, 5, 6, 7 and 9, which are divisible by 5 and none of the digits is repeated?

In a group of 6 boys and 4 girls, four children are to be selected. In how many different ways can they be selected such that at least one boy should be there?

In how many different ways can the letters of the word 'LEADING' be arranged in such a way that the vowels always come together?