ASVAB Study GuideDivisibility Rules for 3 and 9
Converting ∘F to ∘C
$$C = (F - 32) \times \frac{5}{9}$$
Subtract 32 from the Fahrenheit temperature, then multiply by 5 and divide by 9.
Example
Convert 98.6 °F to Celsius.
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1) $$98.6 - 32 = 66.6$$.
2) $$66.6 \times \frac{5}{9} = 37$$ °C.
Practice problems
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Problem 1
Convert 32 °F to Celsius.
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Answer: 0 °C
$$C = (32 - 32) \times \frac{5}{9} = 0 \times \frac{5}{9} = 0$$ °C.
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Problem 2
Convert 68 °F to Celsius.
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Answer: 20 °C
$$C = (68 - 32) \times \frac{5}{9} = 36 \times \frac{5}{9} = 20$$ °C.
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Problem 3
Convert -40 °F to Celsius.
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Answer: $$-40^\circ\text{C}$$
$$C = (-40 - 32) \times \frac{5}{9} = -72 \times \frac{5}{9} = -40^\circ\text{C}$$ (Fahrenheit and Celsius intersect at $$-40^\circ$$).
Remember
Remember to subtract 32 FIRST before multiplying by $$\frac{5}{9}$$ (or dividing by 1.8).