A college has raised 75% of the amount it needs for a new building by receiving an average donation of Rs. 600 from the people already solicited. The people already solicited represent 60% of the people, the college will ask for donations. If the college is to raise exactly the amount needed for the new building, what should be the average donation from the remaining people be solicited?

Correct Answer: 300
Let the number of people be x who has been asked for the donationsPeople already solicited = 60% of x = 0.6xRemaining people = 40% of x = 0.4x Amount collected from the people solicited, = 600 × 0.6x = 360x360x = 75% of the amount collectedRemaining amount = 25% = 120xThus,Average donations from remaining people,$$\eqalign{ & = \frac{{120{\text{x}}}}{{0.4{\text{x}}}} \cr & = 300 \cr} $$