10th Grade Arithmetic and Geometric Sequences Worksheet — Level 1 — Practice Set 4 — Answers
Answer sheet with worked solutions for the 10th Grade sequences & series worksheet.
10th Grade Arithmetic and Geometric Sequences Worksheet — Level 1 — Practice Set 4 — Answers
Arithmetic: Tₙ = a + (n − 1)d. Geometric: Tₙ = arn − 1. Show your work.
1.For the arithmetic sequence 18, 24, 30, 36, …, write the common difference and the rule for the nth term.
Answer: d = 6; Tₙ = 6n + 12
- d = 24 − 18 = 6
- Tₙ = a + (n − 1)d = 18 + (n − 1) × 6 = 6n + 12
2.Find the 13th term of the arithmetic sequence 4, 1, −2, −5, …
Answer: −32
- a = 4, d = −3
- T13 = 4 + 12 × −3 = −32
3.For the arithmetic sequence −1, 2, 5, 8, …, write the common difference and the rule for the nth term.
Answer: d = 3; Tₙ = 3n − 4
- d = 2 − (−1) = 3
- Tₙ = a + (n − 1)d = −1 + (n − 1) × 3 = 3n − 4
4.For the arithmetic sequence 6, 15, 24, 33, …, write the common difference and the rule for the nth term.
Answer: d = 9; Tₙ = 9n − 3
- d = 15 − 6 = 9
- Tₙ = a + (n − 1)d = 6 + (n − 1) × 9 = 9n − 3
5.For the arithmetic sequence 10, 16, 22, 28, …, write the common difference and the rule for the nth term.
Answer: d = 6; Tₙ = 6n + 4
- d = 16 − 10 = 6
- Tₙ = a + (n − 1)d = 10 + (n − 1) × 6 = 6n + 4
6.Find the 30th term of the arithmetic sequence 9, 8, 7, 6, …
Answer: −20
- a = 9, d = −1
- T30 = 9 + 29 × −1 = −20
7.Find the 12th term of the arithmetic sequence −8, −5, −2, 1, …
Answer: 25
- a = −8, d = 3
- T12 = −8 + 11 × 3 = 25
8.Find the 28th term of the arithmetic sequence 10, 15, 20, 25, …
Answer: 145
- a = 10, d = 5
- T28 = 10 + 27 × 5 = 145
9.Find the 12th term of the arithmetic sequence 7, 12, 17, 22, …
Answer: 62
- a = 7, d = 5
- T12 = 7 + 11 × 5 = 62
10.For the arithmetic sequence 4, 9, 14, 19, …, write the common difference and the rule for the nth term.
Answer: d = 5; Tₙ = 5n − 1
- d = 9 − 4 = 5
- Tₙ = a + (n − 1)d = 4 + (n − 1) × 5 = 5n − 1
Marking tips
- Give credit for correct method even when the final answer slips — the working shows where the thinking went right.
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