For 4 digit numbers, we have to arrange the given 5 digits in 4 vacant places. This can be done in 5P4
= 5 × 4 × 3 × 2 = 120 ways.
For 4-digit even numbers, the unit’s place can be occupied by one of the 2 digits 2 or 4. The remaining 4 digits can be arranged in the remaining 3 places in 4P3 ways.
∴ By the multiplication rule, the required number of 4-digit even numbers is 2 × 4P3 = 2 × 4 × 3 × 2 = 48.