LEARN · EXPLAIN · REVISE

A theatre has t rows; the first has 10 seats and each next row has 2 more. Find the total seats.

Read the idea, work independently, then explain what changed.

TOPIC 01

Sequences: mixed review

A mixed assessment: identify the method, justify it and revise your reasoning.

Use one hint at a time. A correction explains what changed, not just the final answer.

01 / Transfer#Your turn

t=33

Skills and prerequisite lessons

Working and explanation

BUILD THE REASONING

Hint 1

Use the common difference and the arithmetic-sum formula.

Hint 2

Use this intermediate relation.

a_t=10+2(t-1)

Worked solution

Use the common difference and the arithmetic-sum formula.
Apply the stated relation and retain its conditions.
$a_t=74$
Apply the stated relation and retain its conditions.
$S_t=33(10+74)/2=1386$
The discrete row count is positive and integral; no continuous rounding is needed.

The requested value is 1386.

Checks and common pitfalls: The discrete row count is positive and integral; no continuous rounding is needed.

Think first. Reveal a hint when the class is ready.

Teacher preparation and assessment