Question

Ravi is putting up a fence in his backyard. He builds 3 units the first day, 7 units the second day and 11 units the third day. If he continues this pattern, how many days will it take him to finish the 55 unit fence?

Answer 1

Each day he puts up 4 more units than the day before.

By the third day he's put up 21 units.
4th day = 15 units = total 36 units
5th day = 19 units = total = 55 units