Question

Find the following sums without operating:

(i) 1 + 3 + 5 + 7
(ii) 1 + 3 + 5 + 7 + 9 + 11 + 13
(iii) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19

Answer 1

Sum of the numbers given is equal to the square of their number

(i) 1 + 3 + 5 + 7 

= 4 sum of numbers 

= (4)² 

= 16

(ii) 1 + 3 + 5 + 7 + 9 + 11 + 13 

= 7 sum of numbers 

= (7)² 

= 49

(iii) 1+3 + 5 + 7 + 9 +11 + 13 + 15 + 17 + 19 

= 10 sum of numbers 

= (10)² 

= 100