PSLE
The graph shows the temperature of water in a pot from 2100 to 21 42.
- For how many minutes was the temperature of the water 55°C and below? Give your answer in min.
- During which two 7-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 2135 to 2142? Give your answer in °C/min.
(a)
Temperature of water that reached 55°C at 21 14.
From 21 14 to 21 42: 28 min
Duration that the temperature of water that reached 55°C and below = 28 min
(b)
Decrease in temperature of water
From 21 00 to 21 07: 79°C - 65°C = 14°C
From 21 7 to 21 14: 65°C - 55°C = 10°C
From 21 14 to 21 21: 55°C - 49°C = 6°C
From 21 21 to 21 28: 49°C - 34°C =
15°C
From 21 28 to 21 35: 34°C - 29°C = 5°C
From 21 35 to 21 42: 29°C - 14°C =
15°C
Two 7-minute intervals that the temperature of water decreas
es at the same rate are 21 21 to 21 28 and 21 35 to 21 28. (c)
Change in temperature per minute from 21 35 to 21 42
= 7 ÷ 7
= 1°C/min
Answer(s): (a) 28 min; (b) 21 21 to 21 28, 21 21 to 21 28; (c) 1°C/min