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The sum of a pair of positive integer is 336 and their H.C.F. is 21. The number of such possible pairs is
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- 2
- 3
- 4
- 5
Correct Option: C
Let the numbers be 21p and 21q where p and q are prime to each other.
∴ 21p + 21q = 336
⇒ 21 (p + q) = 336
| ⇒ p + q = | = 16 | 21 |
∴ Possible pairs = (1 , 15), (5 , 11), (7 , 9), (3 , 13)
Hence , The number of such possible pairs is 4 .
