The number of different 7 digit numbers that can be written using only the three digits 1, 2 and 3 with the condition that the digit 2 occurs twice in each number is
Other than 2, remaining five places are to be filled by by 1 and 3
number of ways for five places = 2 × 2 × 2 × 2 × 2 = 25
For 2, selecting 2 places out of
Required no. of ways .