The number of different seven 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 can be filled by 1 and 3 for each place. The number of ways for five places2×2×2×2×2=25For 2, selecting 2 places out of 7 is  7C2. Hence, for required number of ways is  7C2×25