Ratio and Proportion

Mathematics — First Preparatory

Common mistakes

Writing a ratio between two quantities in different units without converting them. The ratio of 30 cm to 1 m is not 30 : 1.
Confusing a b with b : a. The order of the terms matters.
Multiplying the wrong pairs when checking. The rule is extremes with extremes and means with means, so 4 × 15 is correct and 4 × 6 is not.
Forgetting that a mean proportional is found from a square root, and that the positive value is the one normally asked for.

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