Question : Directions: Select the option that will replace the question mark (?) in the given series.
78, 89, 82, 87, 84, ?
Option 1: 88
Option 2: 86
Option 3: 80
Option 4: 78
Correct Answer: 86
Solution :
Given:
78, 89, 82, 87, 84, ?
Add and subtract alternately the decreasing order of prime numbers.
78 + 11 = 89; 89 – 7 = 82; 82 + 5 = 87; 87 – 3 = 84; 84 + 2 = 86
So, 86 is the missing number of the series. Hence, the second option is correct.
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