Question

(i) How many four digit numbers can be formed in which all the digits are different?
(ii) How many three digit numbers can be formed without using the digits 2, 3, 5, 6,7 and 9?​

Answer 1

Answer:

There will be as many 4-digit numbers as there are permutations of 5 different digits taken 4 at a time. 5 5 4 5 1 P ! ! ! ! = 5 × 4 × 3 × 1 × 1 = 120 Among the 4-digit numbers formed by using the digits, 1, 2, 3, 4, 5, even numbers end with either 2 or 4.