Question

How many 3-digit numbers can be formed by using the digits 0, 1, 3, 5, 7 while each digit may be repeated any number of times?

Answer 1

100’s place 10’s place Unit’s place

There are total 5 digits available, for forming a 3 digit number, in 100’s place only 1,3,5,7 can be used(0 not included because it will lead to formation of 2 digit number.) 

In 10’s place any of the 5 can be used and same is the case with one’s place. 

So total number of 3 digit numbers formed = 4 × 5 × 5 = 100