Question

Use the formula f=9/5c+32 to convert -20 degrees f

Answer 1

c ≈ -29°

Explanation:

To convert Fahrenheit to Celsius using the formula, substitute the degrees for Fahrenheit "f", then isolate Celsius "c".

f =
`(9)/(5)c` + 32

-20 =
`(9)/(5)c` + 32 Substitute "f" for -20

-20 - 32 =
`(9)/(5)c` + 32 - 32 Subtract 32 from both sides

-20 - 32 =
`(9)/(5)c` +32-32 cancels out to 0. Simplify left side

-52 =
`(9)/(5)c`

-52/
`(9)/(5)` =
`(9)/(5)c/(9)/(5)` Divide by 9/5 on both sides

-52/
`(9)/(5)` = c

-52
`*(5)/(9)` = c When dividing a fraction, flip the fraction and change to multiplication

`(-52*5)/(9)` = c Multiply by combining into the numerator

`(-260)/(9)` = c Use a calculator

c = -28.8888888889°

c ≈ -29° Round to the nearest degrees

Therefore -20°F is about -29°C.