A tank loses 21 of its water, then 21 of the water remaining. It now contains 2L. How many litres did it contain initially?
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Answer: 8
The fraction remaining is (21)(21).
Divide 2 by that fraction to obtain 8L.
Example 2
One pump fills a tank in 9 hours, another in 6 hours. Both work together at constant rates. How many hours do they take? Give an exact fraction if needed.
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Answer: 518
Their rates add: 91+61=185 tank per hour.
Take the reciprocal.
Example 3
A tank loses 21 of its water, then 31 of the water remaining. It now contains 6L. How many litres did it contain initially?
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Answer: 18
The fraction remaining is (21)(32).
Divide 6 by that fraction to obtain 18L.
Remaining fractions, rates, recurring decimals and rational relationships practice | Year 8 | Ascent Arcade