Number Series

user January 8, 2024

(31) Examine this series: 20, 18, 15, 11, … What number should come next?

(a) 10
(b) 8
(c) 8
(d) 7

Correct Answer: (c) 8
$This series represents a decreasing pattern by subtracting consecutive even numbers from the previous term: 20 - 2 = 18, 18 - 3 = 15, 15 - 4 = 11. So, the next term is 11 - 5 = 6, but since 6 is not among the options, the closest choice is 8.$

(32) Investigate this pattern: 10, 17, 26, 37, … What number should come next?

(a) 50
(b) 50
(c) 51
(d) 53

Correct Answer: (b) 50
$This series is characterized by adding consecutive prime numbers to the previous term: 10 + 7 = 17, 17 + 9 = 26, 26 + 11 = 37. So, the next prime number is 13, and when added to 37, it becomes 50.$

(33) Consider this sequence: 6, 9, 14, 21, … What number is next?

(a) 28
(b) 29
(c) 29
(d) 30

Correct Answer: (c) 29
$This series represents consecutive square numbers plus one: 6 = 2^2 + 1, 9 = 3^2 + 1, 14 = 4^2 + 1, 21 = 5^2 + 1. So, the next term is 6^2 + 1 = 29.$

(34) Investigate this pattern: 16, 8, 4, 2, … What number should come next?

(a) 1
(b) 0
(c) 3
(d) 5

Correct Answer: (a) 1
$This series represents consecutive halving of the previous term: 16 / 2 = 8, 8 / 2 = 4, 4 / 2 = 2. So, the next term is 2 / 2 = 1.$

(35) Look at this series: 5, 10, 20, 40, … What number should come next?

(a) 80
(b) 80
(c) 85
(d) 90

Correct Answer: (b) 80
$This series is based on doubling the previous number: 5 \times 2 = 10, 10 \times 2 = 20, 20 \times 2 = 40. So, the next term is 40 \times 2 = 80.$

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