Question

Find the sum.

12Σn=1 3n +1

a. 252
b. 234
c. 246

Answer 1

Answer: C

Explanation:

`Method\ 1\\\\\displaystyle \sum _(i=1)^(12) (3i+1)=(((3*12+1)+(3*1+1))*12)/(2) =(37+4)*6=246\\\\Methode\ 2\\\\\displaystyle \sum _(i=1)^(12) (3i+1)=\sum _(i=1)^(12) (1)+3*\sum _(i=1)^(12) (i)=12+3*((12+1)*12)/(2) =12+3*13*6=246\\`

Answer C