Question

A solution is to be kept between 68°F and 77°F. What is the range in temperature in degree Celsius (C) if the Celsius/Fahrenheit (F) conversion formula is given by $F = \frac{9}{5}C + 32\,\, ?$

Answer 1

Since the solution is to be kept between 68°F and 77°F, 68 < F < 77
Putting $F = \frac{9}{5} C + 32$ we obtain
$68 < \frac{9}{5}C+32 < 77$
$⇒ 68-32 < \frac{9}{5}C + 32 < 77-32$
$⇒ 36 < \frac{9}{5}C < 45$
$⇒ 36x\frac{5}{9} < C < 45x\frac{5}{9}$
⇒ 20 < C < 25
Thus, the required range of temperature in degree Celsius is between 20°C and 25°C.