Find the sum.

1 + 3 + 5 + ... + 1743

Express the sum using summation notation.

3 + 12 + 27 + . . . + 75

Question

Find the sum.

1 + 3 + 5 + ... + 1743


Express the sum using summation notation.

3 + 12 + 27 + . . . + 75

anonymous · Answer

$$Sn=(a1+an).n/2$$
an=a1+(n-1).r

anonymous · Answer

Can you find n from the formula?

anonymous · Answer

yes put an as 1743

anonymous · Answer

r is 2

campbell_st · Answer

this is an arithmetic series where you know the 1st and last terms and the common difference

so find the number of terms by using

$$T _{n} = a + ( n - 1) d$$

1743 = 1 + ( n - 1) 2

1743 = 2n - 1

1744 = 2n 

n = 872

to find the sum use

$$s _{n}= n/2[ a + l]$$            a = 1st term l = last term 

$$s _{872}=872/2[1 + 1744]$$

$$s _{872}= 760384$$

anonymous · Answer

My S_872 = 764, 744

anonymous · Answer

Oh,  n = 877

campbell_st · Answer

oops 

$$s _{872}= 872/2[1+1743] = 760384$$

anonymous · Answer

Campell's right! My manual calculation is off :(

campbell_st · Answer

lol... the problem we all have