Sequences and series

find the sum of the arithmetic series

an = 145 , d = 5 , n = 21

• 2001

• 1995

• 1250

• 2458

Find the sum: $\sum_{n=1}^{25}3.5n-7$  

• 962.5

• 77

• 42

• 1050

Find the sum of the series $\sum_{n=1}^{20}\left(3n+2\right)$  

• 33.5

• 67

• 670

• 1340

Find the sum of -4 + 1 + 6 + 11 + ... + 91

• 640

• 320

• 500

• 870

Find n for a series for which a₁=6 , d = 2, and S_n= 50.

• 12

• 8

• 5

• n is located as a subscript of S.

Find the sum:  3 + 8 + 13 + 18 + … + 98 

• 1010
• 140
• 959.5
• 909

What is the formula to find the sum of the first n terms of an arithmetic sequence?

• S = (n/2)(2a + (n-1)d)

• S = (n/2)(2a + d)

• S = n(2a + (n-1)d)

• S = (n/2)(a + (n-1)d)

Determine the 5th partial sum ( $S_5$ )

for the arithmetic series...

11+ 33 + 99 + . . .  

• 1331

• 891

• 143

• 134 469

Evaluate.

• 225

• 140

• 784

• 153

An arithmetic series equals 624. The first term of this series is 3, and the second term is 5. What is the last term in this series?

• 51

• 49

• 50

• 52