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Question
Find all pairs of consecutive odd natural numbers both of which are larger than 10 and their sum is less than 40
Solution
Let the two numbers be x and x + 2
x + x + 2 < 40
⇒ 2x < 38
`(2x)/2 < 38/2`
⇒ x < 19 and x > 10
So x = 11 ⇒ x + 2 = 13
x = 13 ⇒ x + 2 = 15
x = 15 ⇒ x + 2 = 17
When x = 17 ⇒ x + 2 = 19
So the possible pairs are (11, 13), (13, 15), (15, 17), (17, 19)
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