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Sequences and series
5 NET Mathematics questions with answers and explanations.
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What is the sum of the first 6 terms of the geometric series 3 + 6 + 12 + ...?
- 1 96
- 2 189
- 3 192
- 4 381
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What is the 20th term of the sequence 2, 5, 8, 11, ...?
- 1 57
- 2 59
- 3 62
- 4 60
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Correct answer: 59
The nth term is 2 + (n - 1) x 3 = 3n - 1. For n = 20 it is 59.
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What is the arithmetic mean between 4 and 16?
- 1 8
- 2 10
- 3 12
- 4 20
Show answer
Correct answer: 10
The arithmetic mean of two numbers is half their sum: (4 + 16) / 2 = 10.
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What is the geometric mean between 4 and 16?
- 1 8
- 2 10
- 3 64
- 4 6
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Correct answer: 8
The geometric mean is the square root of the product: sqrt(4 x 16) = sqrt(64) = 8.
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What is the sum of the first 10 odd natural numbers, 1 + 3 + 5 + ...?
- 1 55
- 2 90
- 3 100
- 4 110
Show answer
Correct answer: 100
The sum of the first n odd numbers is n^2, so for n = 10 the sum is 100.