Question

The temperature in Toronto at noon during a winter day measured 4°C. The temperature started dropping 2° every hour. Which inequality can be used to find the number of hours, x, after which the temperature will measure below -3°C?

Answer 1

Let x be number of hours,

4-2x = -3
2x = 7
x = 3.5

Hence in 3.5 hours the temperature will be EXACTLY -3*C
Thus for temperature to be BELOW -3*C,

x > 3.5 (ans)

Answer 2

4 - 2x < 3

Explanation:

Given,

The original temperature = 4°C,

Also, the temperature started dropping 2° every hour.

Thus, the total decrements in temperature after x hours = 2x degree,

So, the final temperature after x hours = original temperature - decrements in temperature

= ( 4 - 2x) degree

According to the question,

Final temperature < -3°C,

⇒ 4 - 2x < -3

Which is the required inequality.