Case I: Number of three-digit numbers formed from 2, 3, 4, 5, 6, greater than 400.

100’s place can be filled by any one of the numbers 4, 5, 6. 100’s place digit can be selected in 3 ways.

Since repetition is not allowed, 10’s place can be filled by any one of the remaining four numbers.

∴ 10’s place digit can be selected in 4 ways.

Unit’s place digit can be selected in 3 ways.

∴ Total number of three-digit numbers formed

= 3 × 4 × 3 = 36

Case II: Number of four-digit numbers formed from 2, 3, 4, 5, 6.

Since repetition of digits is not allowed,

1000’s place digit can be selected in 5 ways.

100’s place digit can be selected in 4 ways. 10’s place digit can be selected in 3 ways.

Unit’s place digit can be selected in 2 ways.

∴ Total number of four-digit numbers formed

= 5 × 4 × 3 × 2 = 120

Case III: Number of five-digit numbers formed from 2, 3, 4, 5, 6

 Similarly, since repetition of digits is not allowed,

Total number of five digit numbers formed

= 5 × 4 × 3 × 2 × 1 = 120.

∴ Total number of numbers that exceed 400

= 36 + 120 + 120 = 276