AMO · 2027 · Grades 6-7 · Self-study SET 31 Question 12

A child gets 10 dollars in pocket money each day. He saves 1 dollar on the first day, 2 dollars on the second, 3 dollars on the third, 4 dollars on the fourth, and so on. On which day will he first have enough saved to buy his sister a 50-dollar school bag?

**Input:** Choose one option.