Question

6+13+20+...... +97 find the sum of the following...
Clue: this is an series and sequences chapter, 10th std

Answer 1

Step-by-step explanation:

this is an ap, where d=7, a=6, n= 14

sum = n/2 (2a+(n-1)*d)

= 14/2(2*6+(14-1)*7)

= 7(12+91)= 721

Answer 2

Step-by-step explanation:

a=6

d=7

an=97

An=a+(n-1)d

97=6+(n-1)7

91=7n-7

98=7n

n=98/7

n=14

Sn=n/2(2a+(n-1)d)

S14=14/2(2*6+(14-1)7)

=7(12+13*7)

=7(12+91)

=7*103

S14=721