AlgebraMediumCounting notes of two values
Algebra practice question
A cash box holds 23 notes, all either $5 or $20, worth $250 in total. How many $20 notes are in the box?
Answer: 9
Let x be the number of $20 notes: 5(23 − x) + 20x = 250 → 115 + 15x = 250 → 15x = 135 → x = 9.
Common wrong answers
- If you answered 14
- 14 is the number of $5 notes.
- If you answered 12.5
- 12.5 is 250 ÷ 20, ignoring the $5 notes.
- If you answered 11.5
- 11.5 assumes equal numbers of each.
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