If the ratio of boys to girls is 3:4 and there are 21 boys, how many girls are there?

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Multiple Choice

If the ratio of boys to girls is 3:4 and there are 21 boys, how many girls are there?

Ratio 3:4 means for every 3 boys there are 4 girls. With 21 boys, the number of such groups is 21 ÷ 3 = 7. Each group includes 4 girls, so there are 7 × 4 = 28 girls. This keeps the 3:4 relationship, since 21:28 simplifies to 3:4. Quick checks: if there were 21 girls, the boys would be (3/4)×21 = 15.75 (not a whole number); with 14 girls, the boys would be 10.5; with 24 girls, the boys would be 18. Only 28 girls maintains the ratio with 21 boys.

Ratio 3:4 means for every 3 boys there are 4 girls. With 21 boys, the number of such groups is 21 ÷ 3 = 7. Each group includes 4 girls, so there are 7 × 4 = 28 girls. This keeps the 3:4 relationship, since 21:28 simplifies to 3:4. Quick checks: if there were 21 girls, the boys would be (3/4)×21 = 15.75 (not a whole number); with 14 girls, the boys would be 10.5; with 24 girls, the boys would be 18. Only 28 girls maintains the ratio with 21 boys.

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