AlgebraMediumStarting balance from two later balances
Algebra practice question
A savings account's balance grows by the same amount each month. After 2 months it holds $90 and after 5 months it holds $120. How many dollars did it hold at the start?
Answer: 70
The monthly growth is 30/3 = 10, so the start was 90 − 20 = 70.
Common wrong answers
- If you answered 10
- 10 is the monthly growth.
- If you answered 60
- 60 subtracts 30 from 90.
- If you answered 80
- 80 subtracts only one month's growth.
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