Question

I'll fan and medal
Find the sum of the arithmetic sequence.

-1, 2, 5, 8, 11, 14, 17

Answer 1

what do you think?
any ideas ?

Answer 2

No this is new to me

Answer 3

@mayankdevnani

Answer 4

There are two method to solve this :-
1) Find sum using arithmetic progression formula
2) Simply add them

Answer 5

I can just add them all together?

Answer 6

yeah! this is our second method

Answer 7

Thats what I was going to say was add them all together but I didn't know if there was some catch. :P

Answer 8

57?

Answer 9

56

Answer 10

yeah! 56 is correct

Answer 11

wanna solve it by first method ?

Answer 12

How do you do that?

Answer 13

do you know the formula of summation of arithmetic progression ?

Answer 14

No I don't

Answer 15

If you have given an arithmetic progression with its 1st term and last term,use this formula :-
\[\large \bf S_n=\frac{n}{2}(a+l)\]
where n=number of terms
a=first term
l=last term

Answer 16

given equation :-
-1, 2, 5, 8, 11, 14, 17
where
a=-1
l=17
n=7
\[\large \bf S_7=\frac{7}{2}(-1+17)=\frac{7}{2} \times 16=8 \times 7=56\]

Answer 17

you'll get same answer in each case

Answer 18

That makes sense! Thank you! Can you help me with one more question??

Answer 19

sure :D

Answer 20

I'll open a new question

Answer 21

yea sure