Arithmetic series

Sum the first n terms with the average-of-ends formula, from seats in a theater to staircase blocks.

Standards:F-BF.A.2

Try it: three questions

Real questions from the practice bank. Tap an answer to check it.

Question 1 of 3

A theater has 18 seats in the first row. Each row after has 4 more seats than the row before. How many seats are in the 7th row?

Question 2 of 3

An arithmetic series has first term a = 7 and common difference d = 3. Find the sum of the first 12 terms.

Question 3 of 3

A concert venue sells tickets in blocks. The first day, 150 tickets are sold. Each day after, 25 more tickets are sold than the previous day. How many tickets are sold on the 6th day?

How this fits in

Arithmetic series is one skill in the Sequences & Series unit. Students read the unit lesson, then earn a bronze, silver, or gold medal on their last 10 answers. Medals never go down. A mastered unit comes back for review after 1, 3, 7, 16, and 35 days so it stays learned.

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