AlgebraMediumCounting items of two sizes from a total volume
Algebra practice question
A vending machine holds 90 cans of two sizes, 330 millilitres and 500 millilitres, and the cans contain 36,500 millilitres in total. How many 500-millilitre cans does the machine hold?
Answer: 40
Let x be the number of 500 ml cans, so 90 − x are 330 ml: 330(90 − x) + 500x = 36,500 → 29,700 + 170x = 36,500 → 170x = 6,800 → x = 40.
Common wrong answers
- If you answered 45
- 45 assumes the two sizes are equal in number.
- If you answered 50
- 50 is the number of 330 ml cans (90 − 40).
- If you answered 73
- 73 comes from 36,500 ÷ 500, ignoring the 330 ml cans.
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