5 boys or 9 girls completed a graffiti in 19 days .How long will it take to complete the same graffiti with 3 boys and 6 girls ?
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15 days
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20 days
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36 days
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12 days
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8 days
5 boys = 9 girls. 1 boy = 1.8 girls. 3 boys + 6 girls = 3(1.8) + 6 = 5.4 + 6 = 11.4 girls. 9 girls take 19 days. 11.4 girls take (9 * 19) / 11.4 = 171 / 11.4 = 15 days.
Assume the total work is the least common multiple of 5 and 9, which is 45 units, meaning 1 boy completes 45 over 19 units per day and 1 girl completes 45 over 19 units per day (assuming the phrasing implies equivalence). Wait, 5 boys equal 9 girls, so if total work is 45 boy-days, the daily work of 3 boys and 6 girls equals the daily work of 3 boys plus 6 times (5 over 9) boys, equaling 3 plus 3.33, which is 6.33 boys. Actually, let total work be 5 men times 19 days equaling 95 units; 1 boy does 1 unit and 1 girl does 5 over 9 units daily. The combined daily work of 3 boys and 6 girls is 3 plus 6 times (5 over 9), equaling 3 plus 10 over 3, which is 19 over 3 units per day. Dividing the total work of 95 units by their daily capacity of 19 over 3 yields 15 days to complete the graffiti.