Practice Questions: Number Series | Logical Reasoning (LR) and Data Interpretation (DI) - CAT PDF Download

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Q1: Look at this series: 21, 9, 21, 11, 21, 13, 21, ... What number should come next?
(a) 14
(b) 15
(c) 21
(d) 23
Ans: (b)
Sol: In this alternating repetition series, the random number 21 is interpolated every other number into an otherwise simple addition series that increases by 2, beginning with the number 9.

Q2: Look at this series: 58, 52, 46, 40, 34, ... What number should come next?
(a) 26
(b) 28
(c) 30
(d) 32
Ans: (b)
Sol: This is a simple subtraction series. Each number is 6 less than the previous number.

Q3: Look at this series: 3, 4, 7, 8, 11, 12, ... What number should come next?
(a) 7
(b) 10
(c) 14
(d) 15
Ans: (d)
Sol: This alternating addition series begins with 3; then 1 is added to give 4; then 3 is added to give 7; then 1 is added, and so on.

Q4: Look at this series: 8, 22, 8, 28, 8, ... What number should come next?
(a) 9
(b) 29
(c) 32
(d) 34
Ans: (d)
Sol: This is a simple addition series with a random number, 8, interpolated as every other number. In the series, 6 is added to each number except 8, to arrive at the next number.

Q5: Look at this series: 31, 29, 24, 22, 17, ... What number should come next?
(a) 15
(b) 14
(c) 13
(d) 12
Ans: (a)
Sol: This is a simple alternating subtraction series, which subtracts 2, then 5.

Q6: Look at this series: 28 25 5 21 18 5 14. What number should come next?
(a) 11 5
(b) 5 5
(c) 10 5
(d) 10 5
Ans: (a)
Sol: This is an alternating subtraction series with the interpolation of a random number, 5, as every third number. In the subtraction series, 3 is subtracted, then 4, then 3, and so on.

Q7: Look at this series: 8 11 21 15 18 21 22. What number should come next?
(a) 25 18
(b) 25 21
(c) 25 29
(d) 24 21
Ans: (b)
Sol: This is an alternating addition series, with a random number, 21, interpolated as every third number. The addition series alternates between adding 3 and adding 4. The number 21 appears after each number arrived at by adding 3.

Q8: Look at this series: 9 16 23 30 37 44 51. What number should come next?
(a) 59 66
(b) 56 62
(c) 58 66
(d) 58 65
Ans: (d)
Sol: Here is a simple addition series, which begins with 9 and adds 7.

Q9: Look at this series: 2 8 14 20 26 32 38. What number should come next?
(a) 2 46
(b) 44 50
(c) 42 48
(d) 32 26
Ans: (b)
Sol: This is a simple addition series, which begins with 2 and adds 6.

Q10: Look at this series: 9 11 33 13 15 33 17. What number should come next?
(a) 19 33
(b) 33 35
(c) 33 19
(d) 15 33
Ans: (a)
Sol: In this alternating repetition series, a random number, 33, is interpolated every third number into a simple addition series, in which each number increases by 2.