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Question

Select the number that will come next in the following series.

2, 4, 7, 11, 16, ?

The correct answer is 22

Understanding Number Series and Finding the Next Term

This question asks us to find the next number in the given series: 2, 4, 7, 11, 16, ?.

To solve number series questions, we need to look for a pattern or a rule that connects the terms. This pattern can involve addition, subtraction, multiplication, division, or a combination of operations, often involving the position of the term or the preceding term.

Analyzing the Pattern in the Series

Let's examine the differences between consecutive terms in the series:

  • Difference between the 2nd term (4) and the 1st term (2): $\text{4} - \text{2} = \text{2}$
  • Difference between the 3rd term (7) and the 2nd term (4): $\text{7} - \text{4} = \text{3}$
  • Difference between the 4th term (11) and the 3rd term (7): $\text{11} - \text{7} = \text{4}$
  • Difference between the 5th term (16) and the 4th term (11): $\text{16} - \text{11} = \text{5}$

The sequence of differences is 2, 3, 4, 5. We can observe that the difference between consecutive terms is increasing by 1 each time. This suggests that the next difference in the series will be 6.

Calculating the Next Number in the Series

Following the pattern of differences, the next difference should be 6. To find the next number in the original series, we add this next difference to the last term of the series.

The last term in the series is 16.

The next difference is 6.

Therefore, the next number in the series = Last term + Next difference

Next number = $\text{16} + \text{6} = \text{22}$

So, the next number in the series 2, 4, 7, 11, 16, ? is 22.

Verification using a Table

We can represent the series and the differences in a table:

Term Number Term Value Difference from Previous Term
1st 2 -
2nd 4 $\text{4} - \text{2} = \text{2}$
3rd 7 $\text{7} - \text{4} = \text{3}$
4th 11 $\text{11} - \text{7} = \text{4}$
5th 16 $\text{16} - \text{11} = \text{5}$
6th $\text{16} + \text{6} = \text{22}$ 6

The table clearly shows the pattern in the differences (2, 3, 4, 5, 6), confirming that the next term is 22.

Conclusion

The pattern in the series is that the difference between consecutive terms increases by 1 each time. Applying this pattern, the next term after 16 is found by adding 6 to 16, which gives 22.

Revision Table: Key Concepts for Number Series

Concept Description
Pattern Recognition Identifying the rule that governs the sequence of numbers.
Difference Series Calculating the differences between consecutive terms to find a pattern.
Arithmetic Progression A sequence where the difference between consecutive terms is constant (often applies to the original series or the difference series).
Next Term Prediction Using the identified pattern to calculate the subsequent number in the sequence.

Additional Information: Types of Number Series Patterns

Number series problems can have various patterns. Some common types include:

  • Arithmetic Series: Constant difference between terms (e.g., 3, 6, 9, 12...).
  • Geometric Series: Constant ratio between terms (e.g., 2, 4, 8, 16...).
  • Difference Series: The differences between terms form a pattern (as seen in this problem).
  • Double Difference Series: The differences between the differences form a pattern.
  • Squares or Cubes: Terms are related to squares or cubes of numbers (e.g., 1, 4, 9, 16...).
  • Fibonacci Series: Each term is the sum of the two preceding terms (e.g., 1, 1, 2, 3, 5, 8...).
  • Mixed Series: A combination of two or more patterns.

Solving number series problems often requires careful observation and systematic testing of different potential patterns.

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Important Questions from Number Series

  1. In the following number-pairs, the second number is obtained by applying certain mathematical operations to the first number. Which numbers should replace X and Y so that the pattern followed by the two numbers on the left side of :: is the same as that on the right side of :: ?
    (NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 - Operations on 13 such as adding /subtracting /multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)
    X : 676 :: 17 : Y
  2. Which of the following options should come in place of the question mark (?) in the given series to make it logically complete?
    125, 128, 133, 140, 149,?
  3. What should come in place of the question mark (?) in the given series?
    801 800 792 765 701 ?
  4. What should come in place of the question mark (?) in the given series?
    101 110 121 134 149 ?
  5. What should come in place of the question mark (?) in the given series?
    40, 48, 58, 66, 76, ?
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