The temperature at the foot of a mountain is 20°C. If the mountain is 6,000 metres above sea level, what will…

Analyze the question: The temperature falls as you climb higher. This is the lapse rate, and the question asks for the temperature at the top of a 6,000 m mountain.

Concept: The normal (environmental) lapse rate is about 6.5°C per 1,000 m. Some textbooks round it to 6°C per 1,000 m. WASSCE questions usually use 6.5°C.

Step-by-step solution:

1. Height of the mountain = 6,000 m
2. Temperature drop = (6,000 ÷ 1,000) × 6.5°C = 6 × 6.5 = 39°C
3. Temperature at the top = 20°C − 39°C = −19°C

Check: The question says the temperature is 20°C "at the foot" of the mountain, so I treated 6,000 m as the height gained from the foot to the top. Using 6°C per 1,000 m instead would give 20 − 36 = −16°C (option B). Because the standard rate taught for WASSCE is 6.5°C per 1,000 m, the answer is −19°C.

Answer: A (−19.0°C)

Tip: Remember "6.5 per 1,000". Multiply the height in thousands of metres by 6.5, then subtract the result from the base temperature. Options that are positive, like C and D, can be ruled out at once, since a 6,000 m mountain is far too high for the top to stay warm.