Question

Tyler is saving money to buy some new shoes and putting away money each week. After 3 weeks, he has $19 in his bank and after 9 weeks, he has $31.

On average, how much money did he add to his bank per week?

Answer 1

$2 per a week

Explanation:

When solving this equation, don't immediately divide 19 by three, because we have to pretend at the moment that there may already be money in his account, which shouldn't be included in the growth rate.

So instead, find the rate of change, in our case the common difference from week 3 to 9.

1. Write the rise over run,
   `(31-19)/(9-3)`
2. Subtract,
   `(12)/(6)`
3. Divide to get $2