Question

Find sum of the following series 0.7+0.71+0.72+_ _ _ _ _ _ _ _ to n terms

Answer 1

Sum of n terms=
$sn = \frac{n}{{2} } \times (2a + (n - 1) \\ here \: d = 0.01 \\ a = 0.7 \\ \\ so \: sn = \frac{n}{2} \times (1.4 + (n - 1) \times 0.01) \\ = sn = \frac{n}{2} (1.4 + 0.01n - 0.01) \\ = \frac{n}{2} \times (1.39 + 0.01n) \\ = (0.01 {n}^{2} + 1.39n) \div 2 [Multiplying by 100 for simplicity] \\ =( 1 {n}^{2} + 139n) \div 2 \\ = 0.5{n}^{2} + 69.5n$

Now Equalising by Dividing By 100
=o.oo5n²+0.695n

Hope you Get it...

Regards,
Leukonov