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The average mathematics marks of two Sections A and B of Class IX in the annual examination is 74. The average marks of Section A is 77.5 and that of Section B is 70. The ratio of the number of students of Section A and B is
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- 7 : 8
- 7 : 5
- 8 : 7
- 8 : 5
- 7 : 8
Correct Option: C
If the number of students in section A be p and that in section B be q, then
According to question,
| 74 = | 77.5 × p + q × 70 |
| p + q |
⇒ 74p + 74q = 77.5p + 70q
⇒ 77.5p – 74p = 74q – 70q
⇒ 3.5p = 4q
| ⇒ | p | = | 4 | = | 8 |
| y | 3.5 | 7 |
⇒ p : q = 8 : 7
Hence , The ratio of the number of students of Section A and B is 8 : 7 .
