Inside the Mine Shaft
A mine with levels above and below the ground, marked with integers.
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Levels above the ground are positive, levels below are negative, and the ground is 0.
Write a speed with a direction as an integer, and find where a mine lift or a temperature ends up with start + rate × time.
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Up is +, down is −, and change = rate × time.
In a mining shaft, positions above the ground are positive integers and positions below the ground are negative. The ground is 0.
A mine with levels above and below the ground, marked with integers.
Levels above the ground are positive, levels below are negative, and the ground is 0.
Example 2(a): the elevator goes down from 0 for 60 minutes.
Problem. An elevator in a mining shaft moves 3 metres per minute. It goes down into the shaft from the ground (0). Where will it be after one hour? (Textbook p. 36, Example 2a)
Example 2(b): begin 15 m above ground, go down for 45 minutes.
Problem. The elevator starts going down from 15 m above the ground, at 3 metres per minute. Where is it after 45 minutes? (Textbook p. 37, Example 2b)
Solve the same problem with subtraction, as the book asks.
Textbook p. 37: find the answer to part (b) using Method 1.
In 45 minutes the elevator moves 45 × 3 = metres.
It starts at m and goes down, so we subtract: 15 − 135 = .
The elevator is metres below the ground.
Freezing-room and cold-place temperature problems.
A freezing process lowers a room's temperature from 32°C at 5°C every hour. What is the temperature 10 hours after it begins? (Textbook p. 39, Q2)