Ali : Ahmad = 4 : 1, so let Ali = 4 units, Ahmad = 1 unit.
Difference = 4u − 1u = 3 units.
For them to be equal, Ali must give half the difference to Ahmad.
Amount to give = 3u ÷ 2 = 1.5 units.
Given 1.5 units = 30 marbles, so 1 unit = 30 ÷ 1.5 = 20.
Total marbles = 4u + 1u = 5u = 5 × 20 = 100.
Final Answer: 100