40% of students in school A are girls and remaining 426 are boys. Then,
Total students in school A = 426 * 100/(100 - 40) = 710
Number of girls in school A = 710 - 426 = 284
There are total 2400 students in three schools A, B and C together. Total number of students in school C and B are in the ratio 6: 7 respectively. Then,
Total students in school C = (2400 - 710) * 6/13 = 780
Total students in school B = 780 * 7/6 = 910
Number of girls in school A are 20% less than the number of girls in school C. Then,
Number of girls in school C = 284 * 100/80 = 355
And, number of boys in school C = 780 - 355 = 425
The average of number of boys in school B and C together is 488. Then,
Number of boys in school B = 2 * 488 - 425 = 551
Number of girls in school B = 910 - 551 = 359
In tabular form:
| School | Total students | Boys | Girls |
| A | 710 | 426 | 284 |
| B | 910 | 551 | 359 |
| C | 780 | 425 | 355 |
Here, the average of number of boys in school B and C together = (551 + 425)/2 = 488
And, number of girls in school A = 284
Therefore, ratio = 488: 284 = 122: 71
Study Notes
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