Question

How many 2 digit numbers can be formed from the digits 0, 2, 4, 5, 7 if the repetition of the digits (a) is not allowed (b) is allowed?

Answer 1

Answer:

(a) 16

(b) 20

Step-by-step explanation:

Hi,

Given set of digits are 0, 2, 4, 5, 7

Given hat 2 digit numbers are formed from the above

set of digits

(a) If repetition of digits is not allowed

Tens digit of the 2 digit number cannot take 0, so

we can chose the tens place in 4 different ways,

Units digit of the number can be chosen in 4 different ways,

since the digit in ten's place cannot come in unit's place

also 0 is possible hence, total number of ways of choosing

2 digit numbers are 4 * 4 = 16 [ which includes selection of

tens digit AND selection of units digit]

(a) If repetition of digits is  allowed

Tens digit of the 2 digit number cannot take 0, so

we can chose the tens place in 4 different ways,

Units digit of the number can be chosen in 5 different ways,

since the digit in ten's place can come in unit's place as

well, also 0 is possible hence, total number of ways of choosing

2 digit numbers are 4 * 5 = 20 [ which includes selection of

tens digit AND selection of units digit].

Hope, it helps !