6.
How many 3-digit odd numbers can be formed from the digits 1,2,3,4,5,6 if:
(a) the digits can be repeated (b) the digits cannot be repeated?

(a) Number of digits available = 6
Number of places [(x), (y) and (z)] for them = 3
Repetition is allowed and the 3-digit numbers formed are odd
Number of ways in which box (x) can be filled = 3 (by 1, 3 or 5 as the numbers formed are to be odd)

m = 3
Number of ways of filling box (y) = 6 (∴ Repetition is allowed)

n = 6
Number of ways of filling box (z) = 6 (∵ Repetition is allowed)

p = 6
∴ Total number of 3-digit odd numbers formed
= m x n x p = 3 x 6 x 6 = 108
(b) Number of ways of filling box (x) = 3 (only odd numbers are to be in this box )

m = 3
Number of ways of filling box (y) = 5 (∵ Repetition is not allowed)

n = 5
Number of ways of filling box (z) = 4 (∵ Repetition is not allowed)

p = 4
∴ Total number of 3-digit odd numbers formed
= m x n x p = 3 x 5 x 4 = 60.
231 Views