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Find all pairs of consecutive odd positive integers, both of which are smaller than 10, such that their sum is more than 11.

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Suppose ‘x’ be the smaller of the two consecutive odd positive integers. Now the other odd integer is x + 2.

Given as

Both the integers are smaller than 10 and their sum is more than 11.

Therefore,

x + 2 < 10 and x + (x + 2) > 11

x < 10 – 2 and 2x + 2 > 11

x < 8 and 2x > 11 – 2

x < 8 and 2x > 9

x < 8 and x > 9/2

9/2 < x < 8

Note the odd positive integers lying between 4.5 and 8.

x = 5, 7 [Since, x is an odd integer]

x < 10 [From the given statement]

9/2 < x < 10

Note that, the upper limit here has shifted from 8 to 10. Then, x is odd integer from 4.5 to 10.

Therefore, the odd integers from 4.5 to 10 are 5, 7 and 9.

Then, let us find pairs of consecutive odd integers.

Let x = 5, then (x + 2) = (5 + 2) = 7.

Let x = 7, then (x + 2) = (7 + 2) = 9.

Suppose x = 9, then (x + 2) = (9 + 2) = 11. But, 11 is greater than 10.

Hence, the required pairs of odd integers are (5, 7) and (7, 9)

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