Question

How may four distinct digit numbers can be made out of the digits 1, 2, 3 and 9 which are less than 3000, repetition of the digits being permitted? Select one: a. 72 b. 128 c. 24 d. 144

Answer 1

in 1 st place only 1 and 2 can come

in 2 nd,3rd and 4th place any of the four

So 2× 4× 4×4 = 128

Answer 2

Answer:

(b) 128

Step-by-step explanation:

For the number to be less than 3000,

1st digit can take the value of 1 and 2 only.

2nd, 3rd and 4th can take any of the 4 digits, since repetition is allowed.

Number of possible digits for the 1st digit = 2

Number of possible digits for the 2nd digit = 4

Number of possible digits for the 3rd digit = 4

Number of possible digits for the 4th digit = 4

Find the number of digit numbers:

Total number of digit numbers = 2 x 4 x 4 x 4 = 128

Answer: (b) 128