SOLUTION: out of a tank which is 3/4th full 21 litres of water is drawn out. the tank is now 2/5th full.what is the capacity of tank in litres?

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Question 219413: out of a tank which is 3/4th full 21 litres of water is drawn out. the tank is now 2/5th full.what is the capacity of tank in litres?
Answer by Theo(13342) (Show Source):
You can put this solution on YOUR website!
let T = capacity of the tank when it is full.
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(3/4) * T - 21 = (2/5) * T
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This equation states that three fourths of the tank capacity minus 21 liters equals two fifths of the tank capacity.
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Solve for T:
(3/4) * T - 21 = (2/5) * T
Subtract (2/5) * T and add 21 to both sides of this equation to get:
(3/4) * T - (1/5) * T = 21
Multiply both sides of this equation by 20 to get:
15 * T - 8 * T = 21 * 20
Simplify to get:
7 * T = 21 * 20
Divide both sides of this equation by 7 to get:
T = 21 * 20 / 7
Simplify to get:
T = 60
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The capacity of the tank when it is full is 60 liters.
3/4 * this is 45 liters.
Substract 21 from that to get:
24 liters.
24 liters / 60 = 2/5
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Capacity of the tank is 60 liters. Remove 21 liters from it when it is only 3/4 full and you are left with 24 liters which is 2/5 of the capacity of the tank.
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That's your answer.