Answer:
A) [tex]\frac{n^2}{2} + \frac{n}{2}[/tex]
B) 78
Step-by-step explanation:
B) To find the sum of first 'n' whole numbers , formula used is :-
[tex]\frac{1}{2} ( n^2 + n)[/tex]
We have to find the sum of first 12 whole numbers . So here n = 12
Putting the value of 'n' in above formula ,
[tex]\frac{1}{2} ( 12^2 + 12) \\\\=> \frac{1}{2} ( 144 + 12)\\\\=> \frac{156}{2} = 78[/tex]
Answer:
see explanation
Step-by-step explanation:
A
Given
[tex]S_{n}[/tex] = [tex]\frac{1}{2}[/tex](n² + n) ← multiply each term in the parenthesis by [tex]\frac{1}{2}[/tex]
= [tex]\frac{1}{2}[/tex] n² + [tex]\frac{1}{2}[/tex] n
B
To find the sum of the first 12 whole numbers, substitute n = 12 into the formula, that is
[tex]S_{12}[/tex] = [tex]\frac{1}{2}[/tex] (12² + 12) = [tex]\frac{1}{2}[/tex] (144 + 12) = [tex]\frac{1}{2}[/tex] × 156 = 78
