Question

3.Ifa=2andd=4thenS20 =?(A)600(B)800(C)100(D)400​

Answer 1

Answer:

$Sum = 800 \: or \: option \: b$

Explanation:

Given:

$a_1(first \: term) \: = \: 2$

$d(common \: difference) = 4$

To Find:

$s_{20} \: (sum \: of \: 20 \: terms)$

$Sum \: Formula \: = \: \frac{n}{2} (2a + (n - 1)d)$

$n = number \: of \: terms$

$a = first \: term$

$d = common \: difference$

Substituting the value in the above formula, we get:

$Sum \: = \: \frac{20}{2} (2 \times 2 + (20 - 1)4)$

$Sum = 10(4 + 19 \times 4)$

$Sum = 10 \times 80$

$Sum = 800$

$Sum = 800 \: or \: option \: b$

Additional Information:

AP is a sequence or series of numbers having same difference between numbers. The difference is called common difference.

If the first and last term of a AP is given, we use the below formula :

$Sum \: Formula = \frac{n}{2} (a + l)$

$where$

$a = first \: term$

$l = last \: term$

$n = number \: of \: terms$