PSLE
The graph shows the temperature of water in a pot from 1400 to 14 30.
- For how many minutes was the temperature of the water 45°C and below? Give your answer in min.
- During which two 5-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)
- What was the change in temperature per minute from 1425 to 1430? Give your answer in °C/min.
(a)
Temperature of water that reached 45°C at 14 10.
From 14 10 to 14 30: 20 min
Duration that the temperature of water that reached 45°C and below = 20 min
(b)
Decrease in temperature of water
From 14 00 to 14 05: 73°C - 54°C = 19°C
From 14 5 to 14 10: 54°C - 45°C = 9°C
From 14 10 to 14 15: 45°C - 40°C = 5°C
From 14 15 to 14 20: 40°C - 32°C =
8°C
From 14 20 to 14 25: 32°C - 22°C = 10°C
From 14 25 to 14 30: 22°C - 14°C =
8°C
Two 5-minute intervals that the temperature of water decreas
es at the same rate are 14 15 to 14 20 and 14 25 to 14 20. (c)
Change in temperature per minute from 14 25 to 14 30
= 9 ÷ 5
= 1.8°C/min
Answer(s): (a) 20 min; (b) 14 15 to 14 20, 14 15 to 14 20; (c) 1.8°C/min