Question : Directions: Select the number from among the given options that can replace the question mark (?) in the following series.
21, 23, 20, 22, 19, 21, ?
Option 1: 17
Option 2: 18
Option 3: 23
Option 4: 22
Correct Answer: 18
Solution :
Given:
21, 23, 20, 22, 19, 21, ?
In the above-given series, add 2 and subtract 3 alternately to each number to obtain the next number.
21 + 2 = 23; 23 – 3 = 20; 20 + 2 = 22; 22 – 3 = 19; 19 + 2 =21; 21 – 3 = 18
So, the missing number is 18. Hence, the second option is correct.
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