The graph shows the temperature of water in a pot from 2200 to 22 36.

1. For how many minutes was the temperature of the water 50°C and below? Give your answer in min.
2. During which two 6-minute intervals did the temperature of water decrease at the same rate? Give your answer in the following format. (Eg 01 00 to 01 15, 01 25 to 01 30)
3. What was the change in temperature per minute from 2230 to 2236? Give your answer in °C/min.

(a)
Temperature of water that reached 50°C at 22 12.

From 22 12 to 22 36: 24 min

Duration that the temperature of water that reached 50°C and below = 24 min

(b)
Decrease in temperature of water
From 22 00 to 22 06: 75°C - 65°C = 10°C
From 22 6 to 22 12: 65°C - 50°C = 15°C
From 22 12 to 22 18: 50°C - 33°C = 17°C 
From 22 18 to 22 24: 33°C - 25°C = 8°C 
From 22 24 to 22 30: 25°C - 9°C = 16°C
From 22 30 to 22 36: 9°C - 1°C = 8°C

Two 6-minute intervals that the temperature of water decreases at the same rate are 22 18 to 22 24 and 22 30 to 22 24.

(c)
Change in temperature per minute from 22 30 to 22 36
= 9 ÷ 6
= 1.5°C/min

Answer(s): (a) 24 min; (b) 22 18 to 22 24, 22 18 to 22 24; (c) 1.5°C/min