Problem of the Week
Problem B
Picking Fruit

Kelvin has a part-time job picking apples. Each day, he starts with an empty container, which can hold $960$ apples, and puts the apples that he picks into the container. Kelvin is finished his work for the day if either $3$ hours have passed or he has filled the container.

Kelvin picks $400$ apples on the first day, and each day steadily improves the rate at which he picks apples by picking $21$ more apples than the day before.

After how many days of working can he fill the container in less than $3$ hours?

Theme: Algebra