(4) Sum of the five numbers = 5 × 51 = 255 Sum of the first two numbers = 2 × 38 = 76 Sum of the last two numbers = 2 × 25 = 50 Sum of the five numbers = Sum of the first two numbers + Middle number + Sum of the first two numbers ∴ Middle number = 255 – 76 – 50 = 129