Olympiad Maths Prep

Track / Stage 6 / 382 of 400 #1382 of 2000

Problem 1382

National olympiad, first round
Algebra Difficulty 6.9 Find the answer

The Fahrenheit temperature (FF) is related to the Celsius temperature (CC) by F=95C+32F = \tfrac{9}{5} \cdot C + 32. What is the temperature in Fahrenheit degrees that is one-fifth as large if measured in Celsius degrees?

Official solution

1. We start with the given relationship between Fahrenheit temperature F F and Celsius temperature C C :
F=95C+32 F = \frac{9}{5} \cdot C + 32

2. We need to find the temperature in Fahrenheit degrees that is one-fifth as large if measured in Celsius degrees. This means we need to find F F such that:
F=15C F = \frac{1}{5} C

3. Substitute F=15C F = \frac{1}{5} C into the original equation:
15C=95C+32 \frac{1}{5} C = \frac{9}{5} \cdot C + 32

4. To eliminate the fractions, multiply every term by 5:
C=9C+160 C = 9C + 160

5. Rearrange the equation to isolate C C :
C9C=160 C - 9C = 160
8C=160 -8C = 160

6. Solve for C C :
C=1608 C = \frac{160}{-8}
C=20 C = -20

7. Now, substitute C=20 C = -20 back into the equation F=15C F = \frac{1}{5} C to find F F :
F=15(20) F = \frac{1}{5} \cdot (-20)
F=4 F = -4

The final answer is F=4 \boxed{ F = -4 }

Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic, difficulty and ordering added by this site.