Question

.Calculate the total

a) 1+2 +3+………..+20

b) 3+6+9+…………+60

c) 5 +8 +11+……….+62​

Answer 1

(a) 42

(b) 65

(c) 55

Hope it Helps! Please mark as Brainliest!

Answer 2

◘ Given:-

• a) 1+2+3+....+20
• b) 3+6+9+....+60
• c) 5+8+11+....+62

◘ To Find:-

• Calculate The Total.

$\Large{◘{\underline{\underline{\orange{\bold{Solution:}}}}}}$

For Sum of n Natural Numbers

$\bf{⌘}\;\pink{\bold{S_{n} = \frac{n×(n+1)}{2}}}$

➸ 1+2+3+....+20

$1 + 2 + 3 + .... + 20 \\ 1(1 + 2 + 3 + .... + 20) \\ 1[ \frac{20 \times (20 + 1)}{2} ] \\ 1[ \frac{\cancel{20} \times 21}{\cancel{2}} ] \\ 1(10 \times 21) \\ 210$

• Required Sum ☞ $\red{\bold{210}}$

➸ 3+6+9+....+60

$3 + 6 + 9 + .... + 60 \\ 3(1 + 2 + 3 + .... + 60) \\ 3[\frac{20 \times (20 + 1)}{2} ] \\ 3[ \frac{20 \times 21}{2} ] \\ 3(210) \\ 630$

• Required Sum ☞ $\red{\bold{630}}$

➸ 5+8+11+....+62

$(5 + 8 + 11 + ....+ 62) \\ 1(5 + 8 + 11 + .... + 62) \\ 1[ \frac{60 \times (60 + 1)}{2} ] \\ 1[ \frac{60 \times 61}{2} ] \\ 1 (30 \times 61) \\ 1(1830) \\ 1830$

• Required Sum ☞ $\red{\bold{1830}}$

$\boxed{\tt{@MrSoverign}}$

Hope This Helps!!