Repeated changes, weighted percentages and reverse compound growth
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Practise the method.
Repeated changes, weighted percentages and reverse compound growth
Repeated changes, weighted percentages and reverse compound growth
Example 1
Group A has 120 members, 5% of whom cycle. Group B has 200 members, 60% of whom cycle. What percentage of the combined group cycles? Give an exact fraction if needed.
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Answer: 8315
Count cyclists, add the counts
divide by 320 and multiply by 100:8315%.
Example 2
A price of $6600 increases by r%, then decreases by r%, leaving $6431.04. Find the positive percentage r.
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Answer: 16
The final multiplier is 1−10000r2.
Thus r2=256;
take the positive square root, 16.
Example 3
Group A has 160 members, 30% of whom cycle. Group B has 240 members, 85% of whom cycle. What percentage of the combined group cycles? Give an exact fraction if needed.
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Answer: 63
Count cyclists, add the counts
divide by 400 and multiply by 100:63%.
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