Question -
Answer -
2.
Given:
Both the natural numbers are greater than 10 and their sum is less than 40.
So,
x > 10 and x + x + 2 <40
x > 10 and 2x < 38
x > 10 and x < 38/2
x > 10 and x < 19
10 < x < 19
From this inequality, we can say that x lies between 10 and 19.
So, the odd natural numbers lying between 10 and 19 are 11, 13, 15 and 17. (Excluding 19 as x < 19)
Now, let us find pairs of consecutive odd natural numbers.
Let x = 11, then (x + 2) = (11 + 2) = 13
Let x = 13, then (x + 2) = (13 + 2) = 15
Let x = 15, then (x + 2) = (15 + 2) = 17
Let x = 17, then (x + 2) = (17 + 2) = 19.
x = 11, 13, 15, 17 [Since, x is an odd number]
∴ The required pairs of odd natural numbers are (11, 13), (13, 15), (15, 17) and (17, 19)