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The number of pairs lying between 40 and 100 with their H.C.F as 15 is:
- A3
- B4
- C5
- D6
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CCommunity
Numbers with H.C.F 15 must contain 15 as a factor.
Multiples of 15 between 40 and 100 = 45, 60, 75 and 90
Number of pairs with H.C.F 15 are (45, 60), (45, 75)(60, 75) and (75, 90)
H.C.F of (60, 90) is 30 and that of (45, 90) is 45.
∴ The number of such pairs is 4.
Multiples of 15 between 40 and 100 = 45, 60, 75 and 90
Number of pairs with H.C.F 15 are (45, 60), (45, 75)(60, 75) and (75, 90)
H.C.F of (60, 90) is 30 and that of (45, 90) is 45.
∴ The number of such pairs is 4.