The second number in the given number-pairs is obtained by performing certain…
2023
The second number in the given number-pairs is obtained by performing certain mathematical operation(s) on the first number. The same operation(s) is/are followed in all the number-pairs except one. Find that odd number-pair.
- A.
15 : 34
- B.
1 : 6
- C.
7 : 18
- D.
18 : 42
Attempted by 25 students.
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Correct answer: D
In an ‘odd number-pair’ question, every consistent pair is linked by the same fixed arithmetic operation applied to the first number to produce the second number; the one pair that does not satisfy that shared operation is the odd pair.
Test the relation second number = 2 × first number + 4 on 15 : 34: 2 × 15 + 4 = 34 — matches.
Apply the same relation to 1 : 6: 2 × 1 + 4 = 6 — matches.
Apply the same relation to 7 : 18: 2 × 7 + 4 = 18 — matches.
Apply the same relation to 18 : 42: 2 × 18 + 4 = 40, but the given second number is 42 — does not match.
Since three independent pairs (15 : 34, 1 : 6, and 7 : 18) all confirm the relation second number = 2 × first number + 4, and only 18 : 42 fails this check (it would need to read 18 : 40 to fit), the break in the pattern is confirmed rather than a coincidence.
Therefore, 18 : 42 is the odd number-pair.