Question:medium

Identify the missing number:
1 and 3, 4 and 6, 7 and 9, …. and 12

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In pattern problems, first check the difference between numbers in the same position in each pair. Then extend that pattern to predict the next number.
Updated On: Jul 15, 2026
  • 10
  • 11
  • 12
  • 13
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The Correct Option is A

Approach Solution - 1

Step 1: Look at the second number of each pair: 3, 6, 9, 12. Each term is 3 more than the one before it, so this sequence is consistent on its own.

Step 2: Look at the first number of each pair: 1, 4, 7, and the missing value. Since the second numbers increase by 3 each time, the first numbers should follow the same step of 3, giving 1, 4, 7, 10.

Step 3: Check the gap inside each pair: 3 minus 1 is 2, 6 minus 4 is 2, 9 minus 7 is 2. For the last pair to match this same gap of 2, the first number must be 12 minus 2, which is 10. \[ \boxed{10} \]
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Approach Solution -2

Adding the two numbers within each pair reveals another pattern worth checking, alongside just extending the sequence directly. The sums of the first three pairs are \( 1 + 3 = 4 \), \( 4 + 6 = 10 \), and \( 7 + 9 = 16 \), each 6 more than the one before, so the fourth pair's sum should be \( 16 + 6 = 22 \). Since the second number of the fourth pair is given as 12, the first number must satisfy first plus 12 equals 22. Let's check each option against this sum.

  1. 10: gives a pair sum of \( 10 + 12 = 22 \), exactly matching the expected next sum in the pattern.
  2. 11: gives a sum of 23, breaking the steady increase of 6 between consecutive sums.
  3. 12: gives a sum of 24, also off the expected value of 22.
  4. 13: gives a sum of 25, further from the expected 22 than any other option.

Only 10 keeps the pair-sum pattern increasing by a steady 6 each time.

Therefore, the correct answer is 10.

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