Question

The temperature at 12 noon was 10°c above zero.If it decreases at the rate of 2°c per hour until midnight,at what time the temperature be 8°c below zero? What would be the temperature at midnight?

Answer 1

T₀ = 10° C

d = -2° C

Let Tₙ be -8° C

Now,

Tₙ = T₀ + (n-1) d       [nth term of an AP]

-8 = 10 + (n-1)(-2)

-8 = 10-2n+2

12-2n = -8

2n=20

n=10

Hence, temperature at 10 pm will be 8°C below zero.

Temperature at midnight = T₁₂ = 10 +(12-1)(-2) =10 -22  °C = -12°C