Example

Converting 66 Inches to Feet Using a Conversion Factor

To convert 6666 inches to feet, two conversion factors can be formed from the fact that 11 foot =12= 12 inches: 1 foot12 inches\frac{1 \text{ foot}}{12 \text{ inches}} and 12 inches1 foot\frac{12 \text{ inches}}{1 \text{ foot}}. Both fractions equal 11, but only one will eliminate the unwanted unit.

The correct choice places the unit being converted from (inches) in the denominator so that it cancels with the inches in the original measurement:

66 inches×1 foot12 inches=6612 feet=5.5 feet66 \text{ inches} \times \frac{1 \text{ foot}}{12 \text{ inches}} = \frac{66}{12} \text{ feet} = 5.5 \text{ feet}

The inches in the numerator and denominator cancel — just as common numerical factors do in a fraction — leaving only feet. Multiplying instead by 12 inches1 foot\frac{12 \text{ inches}}{1 \text{ foot}} would not cancel any units and would produce a meaningless result. The strategy is to treat unit labels like algebraic factors: place the unwanted unit where it will divide out, and the desired unit where it will remain.

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Updated 2026-04-21

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