Bill weighs 80 kilograms and is gaining 2 kilograms each month. Phil weighs 65 kilograms and is gaining 5 kilograms each month. How many months, m, will it take for Bill to weigh the same as Phil?
Using the formula for the nth term of an arithmetic sequence we can write: 80 + (n - 1)2 = 65 + (n - 1)5 80 + 2n - 2 = 65 + 5n - 5 3n = 18 n = 6 The answer is 6 months.
