Question

Please select the best answer from the choices provided

A
B
C
D

Answer 1

ANSWER


C.


`\sum_(k=4)^9(5k+3) = 23 + 28 + 33 + 38 + 43+ 48 = 213`


EXPLANATION

The given series is



`\sum_(k=4)^9(5k+3)`
The symbol stands for summation, so we are adding from k=4 to k=9.

We substitute k=4 to k=9 to obtain,




`\sum_(k=4)^9(5k+3) = (5 * 4 + 3) + (5 * 5 + 3) + (5 * 6 + 3) + (5 * 7 + 3) + (5 * 8 + 3) + (5 * 9 + 3)`


We simplify to obtain,


`\sum_(k=4)^9(5k+3) = (20 + 3) + (25 + 3) + (30 + 3) + (35 + 3) + (40 + 3) + (45+ 3)`

This implies that,



`\sum_(k=4)^9(5k+3) = 23 + 28 + 33 + 38 + 43+ 48`



`\sum_(k=4)^9(5k+3) = 213`



The correct answer is C.

Answer 2

C

Explanation:

The summation basically means to plug in k=4, 5, 6, 7, 8, and 9 into the formula part
`5k+3` and sum all of them up. So it becomes:

`(5(4)+3)+(5(5)+3)+(5(6)+3)+(5(7)+3)+(5(8)+3)+(5(9)+3)\\=23+28+33+38+43+48\\=213`

As seen from the work shown, C is the right answer.