Arithmetic sequences and series Quiz

1. An arithmetic sequence has $u_5=18$ and $u_9=34$. Find $d$.

• A. $3$
• B. $4$
• C. $5$
• D. $16$

2. Find $1+2+3+\cdots+40$.

• A. $800$
• B. $840$
• C. $780$
• D. $820$

3. Find $\sum_{r=1}^{20}(3r+2)$.

• A. $670$
• B. $630$
• C. $610$
• D. $1260$

4. An arithmetic series has $a=10$ and $d=-3$. For which value of $n$ is $S_n$ greatest?

• A. $3$
• B. $13$
• C. $4$
• D. $5$

5. Which expression gives the sum of terms $8$ to $15$ of an arithmetic series?

• A. $S_{15}-S_8$
• B. $S_{14}-S_7$
• C. $S_{15}-S_9$
• D. $S_{15}-S_7$