alleryWhich prime follows 13 in the list 2, 3, 5, 7, 11, 13?
- 15
- 17
- 19
- 21
Show answer and solution
Correct answer: B. 17
The series lists primes in order, and the prime after 13 is 17 because 15 is divisible by 3.
RRB NTPC Number Series — practice questions — page 2
Explore 61 free Number Series questions in RRB NTPC Reasoning. Open each question or exercise to read its content, reference answers and available explanation.
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Showing questions 31–60 of 61.
Which prime follows 13 in the list 2, 3, 5, 7, 11, 13?Read the answer and worked solution →Squares of the first four primes are 4, 9, 25, 49. What is the fifth?Read the answer and worked solution →Products of neighbours give 2, 6, 12, 20, 30. Which product comes after?Read the answer and worked solution →A cell count goes 3, 6, 12, 24, 48 as it divides. What is the next count?Read the answer and worked solution →A bacteria sample reads 5, 10, 20, 40 at hourly intervals. What is the next?Read the answer and worked solution →Water level drops 100, 90, 80, 70 cm per day. Predict the next level.Read the answer and worked solution →Gaps rise by one in 1, 2, 4, 7, 11, 16. What number should come after?Read the answer and worked solution →Each number is a perfect square less one: 0, 3, 8, 15, 24. Next number?Read the answer and worked solution →Multiplying by 2, 3, 4, 5 in turn gives 1, 2, 6, 24, 120. What follows?Read the answer and worked solution →A tailor cuts 7 m, 14 m, 21 m, 28 m pieces. How long is the next piece?Read the answer and worked solution →Dividing by 3 each time gives 729, 243, 81, 27. What is the next value?Read the answer and worked solution →Powers n to the n for n = 1, 2, 3, 4 give 1, 4, 27, 256. What is n = 5?Read the answer and worked solution →Cube plus one for 1, 2, 3, 4 gives 2, 9, 28, 65. Which value is next?Read the answer and worked solution →Double and add one at each step: 1, 3, 7, 15, 31. Which number is next?Read the answer and worked solution →After 23 in the sequence 11, 13, 17, 19, 23, which prime is next?Read the answer and worked solution →Increments 3, 4, 5, 6 produce 10, 13, 17, 22, 28. What number is next?Read the answer and worked solution →A series begins 3, 4, 6, 9, 13, 18 with growing gaps. What is its next term?Read the answer and worked solution →After 1, 2, 3, 5, 8, 13, 21 the pattern adds the last two. What is next?Read the answer and worked solution →A coin stack is 2, 4, 8, 16, 32 in size by successive doubling. What next?Read the answer and worked solution →Gaps of 5, 10, 15, 20 build 6, 11, 21, 36, 56. Which number is next?Read the answer and worked solution →Four is added each time: 8, 12, 16, 20. Which term follows?Read the answer and worked solution →One entry is hidden in 2, ?, 12, 20, 30. What is the hidden number?Read the answer and worked solution →Running totals of squares give 1, 5, 14, 30, 55. What is the next total?Read the answer and worked solution →Which square number is the sum of triangular numbers 6 and 10?Read the answer and worked solution →What does the Fibonacci pattern give after the pair 8 and 13?Read the answer and worked solution →A prime is missing in the list 2, 3, 5, ?, 11, 13. Which one?Read the answer and worked solution →Spot the intruder among the numbers 1, 4, 9, 16, 20, 25.Read the answer and worked solution →Triangle dots run 1, 3, 6, 10, 15, 21, 28. How many are in the next?Read the answer and worked solution →Subtracting 1, 2, 3, 4 in turn from 20 gives 20, 19, 17, 14, 10. Next?Read the answer and worked solution →Odd gaps 3, 5, 7, 9 link 4, 7, 12, 19, 28. Which number comes next?Read the answer and worked solution →
Worked practice questions
Squares of the first four primes are 4, 9, 25, 49. What is the fifth?
- 169
- 100
- 81
- 121
Show answer and solution
Correct answer: D. 121
The terms are squares of the primes 2, 3, 5 and 7, so the next is 11 squared, which is 121.
Products of neighbours give 2, 6, 12, 20, 30. Which product comes after?
- 48
- 42
- 44
- 40
Show answer and solution
Correct answer: B. 42
The gaps are 4, 6, 8, 10, so the next gap is 12 and 30 + 12 = 42.
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