(i)
1 + 3 = 4
5 + 11 = 16
21 + 47 = 68
An odd number + another odd number = An Even number
From this observation, we conclude that the sum of any two odd numbers is always an even number.
(ii)
5 × 3 = 15
7 × 9 = 63
11 × 13 = 143
An odd number × Another odd number = An odd number
From this observation, we conclude that “the product of any two odd numbers is always an odd number.”
(iii) Take the odd number 5 and the even number 10
Their sum = 5 + 10 = 15, which is odd.
∴ Sum of an odd number and an even number is always an odd number.
(iv) Take the odd number 5 and the even number 10.
Their product = 5 × 10 = 50, which is even
Thus the product of an odd and an even number is always an even number.
(v) Consider 7 × 5 × 3
We know that the product of any two odd numbers is an odd number
7 × 5 = 35, odd number.
Also we have 35 × 3 = 105
∴ 7 × 5 × 3 = 105, an odd number.
So the product of three odd numbers is always an odd number.