AlgebraEasy–MediumDirect proportion
Algebra practice question
The quantity y is directly proportional to x, and y = 12 when x = 5. What is the value of y when x = 20?
Answer: 48
y = kx with k = 12/5. At x = 20: y = (12/5)(20) = 48.
Common wrong answers
- If you answered 3
- 3 comes from 12 ÷ 4, dividing instead of multiplying.
- If you answered 27
- 27 adds 15 to 12, treating the relationship as additive.
- If you answered 60
- 60 is 12 × 5.
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