10 people went to a restaurant to have a meal as a group. Of these, 9 had already contributed Rs 400 each, while the 10th person had to give the entire additional amount required to honour the restaurant's bill. How much did this person pay if he had to pay Rs 900 more than the group's average?
Step-by-step Solution:
Let the average contribution of the 10 people be $A$. The total bill is $10A$. The first 9 people paid Rs 400 each, so their total is $9 \times 400 = 3600$. The 10th person paid Rs 900 more than the average, so he paid $A + 900$. The sum of all contributions equals the total bill: $$ 3600 + (A + 900) = 10A $$ $$ 4500 + A = 10A $$ $$ 9A = 4500 \implies A = 500 $$ The 10th person paid $A + 900$: $$ 500 + 900 = 1400 \text{ Rs} $$