Rule of three — direct and inverse proportion
Rule of three
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Read the problem. Decide whether the relationship is direct or inverse, then write the answer.
If 3 notebooks cost £12, how much do 7 notebooks of the same kind cost?
Tip: more of one → more of the other (direct proportion).
What does the generator do?
The generator picks two direct-proportion scenarios (price, fuel) and two inverse ones (workers/days, speed/time) and numbers chosen so the answer is always a whole number.
How to solve
For direct proportion: if quantity A is multiplied by k then quantity B is multiplied by k as well. For inverse proportion: if A is multiplied by k then B is divided by k. The product A · B stays constant for inverse proportion.
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