All Exams Test series for 1 year @ ₹349 only
Question

Select the number from among the given options that can replace the question mark (?) in the following series.
40, 36, 33, 31, ?

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
30

Series Pattern Analysis

Examine the differences between consecutive numbers in the series: 40, 36, 33, 31.

  • The difference between the first and second term is:

    $40 - 36 = 4$

  • The difference between the second and third term is:

    $36 - 33 = 3$

  • The difference between the third and fourth term is:

    $33 - 31 = 2$

The differences are 4, 3, and 2. This shows a pattern where the difference decreases by 1 at each step.

Finding the Missing Number

Following the identified pattern, the next difference should decrease by 1 again, becoming 1.

To find the missing number, subtract this next difference (1) from the last number in the series (31):

$31 - 1 = 30$

Therefore, the number that replaces the question mark is 30.

Was this answer helpful?

Similar Questions

  1. What should come in place of the question mark (?) in the given series?
    3, −2, −12, −32, −72, ?
  2. What should come in place of the question mark (?) in the given series?
    512 513 505 532 468 ?
  3. Identify the number that does NOT belong to the following series.
    14, 19, 26, 35, 44, 59
  4. Select the number from among the given options that can replace the question mark (?) in the following series.
    16, 25, 36, 49, ?
  5. Select the number from among the given options that can replace the question mark (?) in the following series.

     5, 18, 39, 68, 105, ?

  6. Select the number that can replace the question mark (?) in the following series.
    14, 2, 28, 3, 84, 4, ?
  7. What should come in place of the question mark (?) in the given series?

    991 990 992 991 993 992 994 ?
  8. What should come in place of the question mark (?) in the given series?

    112 101 90 79 68 ?
  9. What should come in place of the question mark (?) in the given series?

    4 8 24 96 ? 2880
  10. Select the number from among the given options that can replace the question mark (?) in the following series.

    256, 625, 1296, 2401, ?

Important Questions from Number Series

  1. What will come in place of question mark (?) in the following number series?

    2, 5, 11, 23, 44, 77, ?

  2. What will come in place of question mark (?) in the following number series?

    31, 32, 36, ?, 61, 86

  3. What will come in the place of question mark (?) in the following number series?

    3, 6, 18, ?, 630, 6930

  4. What should come in place of the question mark ‘?’ in the following number series?

    60, 40, 50, ?, 180, 460

  5. A series is given with one term wrong. Select that wrong term from the given alternatives.

    J12, M24, P48, S96, U192

Need Expert Advice?
Upcoming Exams
RRB Technician
October 06, 2026
RRB JE
October 27, 2026
RRB ALP
November 03, 2026
Test Series
RRB NTPC img
Railways
RRB NTPC Under Graduate 2026 New Mock Test Series
1580 Tests 2 Tests Free
544 Attempts
4.3(498)
English, Hindi, Telugu +7 More

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App