The mean temperature of Monday–Wednesday is 37°C and of Tuesday–Thursday is 34°C. If Thursday's temperature is 4/5 of Monday's, what is Thursday's temperature?

Introduction / Context:
Overlapping averages with a ratio relation let us set linear equations. Here, two 3-day means and a link between Monday and Thursday produce solvable equations for the daily values needed.

Given Data / Assumptions:

• (M + T + W) / 3 = 37 ⇒ M + T + W = 111
• (T + W + Th) / 3 = 34 ⇒ T + W + Th = 102
• Th = (4/5) * M

Concept / Approach:
Subtract the second sum from the first to relate M and Th, then use the ratio to solve M and hence Th.

Step-by-Step Solution:

Verification / Alternative check:
Plug into sums: T + W + 36 = 102 ⇒ T + W = 66; M + T + W = 45 + 66 = 111, consistent with the first equation.

Why Other Options Are Wrong:
35.5°C, 34°C, 36.5°C: Do not satisfy both the overlap sums and the 4/5 relation simultaneously.

Common Pitfalls:
Using 4/5 of Tuesday instead of Monday, or averaging the two means (37 and 34) directly without respecting overlaps.

Final Answer:
36°C