Q 11-10-037NEETJEE MainEasy
At what temperature do the Celsius and Fahrenheit scales give the same reading?
Answer: (D) $-40°$
Concept. $F = \dfrac95C + 32$. Set $F = C = x$.
Step 1. Solve.
$$x = 1.8x + 32 \;\Rightarrow\; -0.8x = 32 \;\Rightarrow\; x = -40$$
Answer. $-40°$ (Option D).
Solution by Sreeraj P, M.Sc Physics