There was a fundraising effort for a party being organized by John

Solution:

Since the average contribution of all the people was $50, the 60% of the people who contributed 80% of the funds must have contributed an average of more than $50 (since the percentage of funds was greater than the percentage of people), and therefore, the remaining 40% of the people must have contributed an average of less than $50. Since $25 is the only choice that is less than $50, choice E is the correct answer.

Alternate Solution:

Let’s assume that 10 people attended the fund-raiser. We see that the total amount of money collected was 10 x 50 = $500. Since 60% of the attendees donated 80% of the contributions, then 10 x 0.6 = 6 people contributed 500 x 0.8 = $400. This tells us that the remaining 4 people contributed $100. Thus, the average contribution of this group (the remaining 40% of attendees) was 100/4 = $25.

Answer: E

Let , total people attended = 100*x
Total fund raised = 100*y
60*x people contributed 80*y funds.
Hence 40*x people contributed 20*y funds.
Average contribution made by 40*x people = 20*y / 40*x

100x people contributed 100*y funds.
Hence given , 100*y / 100*x = 50
y/x = 50

Hence , Average contribution made by 40*x people = 20*y / 40*x = 1/2 * 50 = 25 Ans..