# Math Help - changing variable

1. ## changing variable

An old way of measuring temperature was the Fahrenheit scale. To change a measurement in Fahrenheit degrees into Celsius, you multiplied the number of Fahrenheit degrees by 5, subtract 160 from your answer, and divided that answer by 9. What would 40 degrees Celsius be in Fahrenheit degrees
a)104 b)86 c)779 7/9 d)4 4/9

2. Originally Posted by kl050196
An old way of measuring temperature was the Fahrenheit scale. To change a measurement in Fahrenheit degrees into Celsius, you multiplied the number of Fahrenheit degrees by 5, subtract 160 from your answer, and divided that answer by 9. What would 40 degrees Celsius be in Fahrenheit degrees
a)104 b)86 c)779 7/9 d)4 4/9
From the problem description, you may produce the conversion formula

$^\circ C=\frac{\left[5(^\circ F)-160\right]}9.$

If you solve for $^\circ F$ you will then have the formula to convert from Celsius to Fahrenheit. Then set $^\circ C=40.$