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Question

The two missing terms (?, ?) in the following series

10, 7, 6, 8, 5, 4, ?, ? are respectively

The correct answer is 6 and 3

In number series questions, our goal is to identify the underlying pattern or rule that governs the sequence of numbers. Once the pattern is discovered, we can apply it to find the missing terms. Let's carefully analyze the given series to determine the relationship between consecutive numbers.

Series Analysis: Uncovering the Pattern

The given number series is:

\(10, 7, 6, 8, 5, 4, ?, ?\)

Let's examine the operations performed between successive terms in the series:

  • From the first term (\(10\)) to the second term (\(7\)): \(10 - 3 = 7\). So, the operation is -3.
  • From the second term (\(7\)) to the third term (\(6\)): \(7 - 1 = 6\). So, the operation is -1.
  • From the third term (\(6\)) to the fourth term (\(8\)): \(6 + 2 = 8\). So, the operation is +2.
  • From the fourth term (\(8\)) to the fifth term (\(5\)): \(8 - 3 = 5\). So, the operation is -3.
  • From the fifth term (\(5\)) to the sixth term (\(4\)): \(5 - 1 = 4\). So, the operation is -1.

Let's list these operations sequentially:

\(-3, -1, +2, -3, -1\)

Upon observing these operations, we can identify a clear repeating pattern. The sequence of operations \(\left(-3, -1, +2\right)\) seems to repeat.

Identifying the Repeating Operations

The pattern of operations identified is a cycle of three steps: subtract 3, then subtract 1, then add 2. This cycle then repeats.

Current Term Operation Applied Next Term
\(10\) \(-3\) \(7\)
\(7\) \(-1\) \(6\)
\(6\) \(+2\) \(8\)
\(8\) \(-3\) \(5\)
\(5\) \(-1\) \(4\)

As shown in the table, the operations \(-3, -1, +2\) complete one cycle, and then the next cycle begins with \(-3, -1\). The series reaches \(4\) after the \(-1\) operation of the second cycle.

Calculating the Missing Terms

To find the next two missing terms, we need to continue the established pattern:

  1. The last operation applied was \(-1\), which resulted in the term \(4\). According to the repeating pattern \(\left(-3, -1, +2\right)\), the next operation after \(-1\) should be \(+2\).
  2. First Missing Term: Apply \(+2\) to the last known term, which is \(4\).

    \(4 + 2 = 6\)

    So, the first missing term is \(6\).

  3. After the \(+2\) operation, the pattern cycle \(\left(-3, -1, +2\right)\) restarts. So, the next operation in the sequence will be \(-3\).
  4. Second Missing Term: Apply \(-3\) to the newly found term, which is \(6\).

    \(6 - 3 = 3\)

    So, the second missing term is \(3\).

Therefore, the two missing terms in the series are \(6\) and \(3\) respectively.

The complete series becomes:

\(10, 7, 6, 8, 5, 4, 6, 3\)

This detailed analysis confirms that the pattern is consistent throughout the series, allowing us to accurately predict the missing values.

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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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