Question

Find the sum (6 + 15 + 24 +33 + .... +105)​

Answer 1

Answer:

Here a=6;d=15-6=9;l=105

Step-by-step explanation:

hope it's help you

Answer 2

Answer:

The sum is $666$.

Step-by-step explanation:

The given series is:

$6 + 15 + 24 +33 + .... +105$

First term is $a=6$

Common difference $d=9$

It is an AP.

AP stands for arithmetic progression.

It is a sequence of numbers in order, in which the difference between any two consecutive numbers is a constant value.

The last term is $l=105$

Mathematically

$l=a+(n-1)d$

Using values

$105=6+(n-1)9$

$105=6+9n-6=9n-3$

$n=108/9=12$

Number of terms are $12$

Sum of twelve terms are:

$S=\frac{n}{2}(a+l)$

$S=\frac{12}{2}(6+105)$

$S=111*6=666$

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