Let each person needs x amount.
Amount 2 people would need = 2x
Amount 5 people would need = 5x
Given 300 (=2x) is enough for 2 people.
HOOK: By what ratio, 2x must increase by to give 5x.
Now 2x needs to be increased in the ratio 2:5 to give 5x.
=> ₹ 300 must increase in the ratio 2:5.