Diagram given - Tank A, 60 cm by 10 cm by 40 cm, with a tap above it, was empty.
Diagram given - Tank B, 50 cm by 20 cm by 36 cm, with a tap above it, was filled with water.
At first, Tank A was empty and one third of Tank B was filled with water. Both taps were turned on at the same time and water from both taps flowed at the same rate of 1.2 litres per minute.
How long did it take for the height of the water to be the same in both tanks?
(1 litre = 1000 cm³)
1/3 x 36 = 12
60 x 10 x H --> 50 x 20 x (H - 12)
1000 H - 600 H --> 12 000
H --> 12 000 / 400 = 30
60 x 10 x 30 = 18 000
18 000 / 1 200 = 15 minutes
It took 15 minutes.
Alternative method
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60 x 10 : 50 x 20 = 3 : 5
2 u --> 1/3 x 36 = 12 cm
5 u --> 5/2 x 12 = 30 cm
60 x 10 x 30 ÷ 1200 = 15 cm
It took 15 minutes.
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it was an exact method i did. i think it is some kind of an easy paper
ReplyDeleteah i write 20 minutes damn
ReplyDeleteAs appeared in PSLE 2010 exam:
ReplyDeleteThere were 2 diagrams for this question.
First diagram showing tank A with a tap above it and at the left hand corner. Dimensions: 60 cm (L) x 10 cm (B) x 40 cm (H). Tank A was emptied.
2nd diagram showing tank B with a tap above it and at the left hand corner.
Dimensions: 50 cm (L) x 20 cm (B) x 36 cm (H). Tank B was filled with water.
At first, Tank A was empty and one third of Tank B was filled with water. Both taps were turned on at the same time and water from both taps flowed at the same rate of 1.2 litres per minute.
How long did it take for the height of the water to be the same in both tanks?
(1 litre = 1000 cm³)