Find the missing number in the given number series:1, 2, 6, 7, 21, 22, 66, 67, ?

Tip:

Through observations, we can see that consecutive numbers are in pairs and second number of a pair is multiplied with 3 to get the next pair. So the missing number would be 67 × 3 = 201

Detailed solution:

The series follows the following pattern:

⇒ 1 + 1 = 2

⇒ 2 × 3 = 6

⇒ 6 + 1 = 7

⇒ 7 × 3 = 21

⇒ 21 + 1 = 22

⇒ 22 × 3 = 66

⇒ 66 + 1 = 67

∴ 67 × 3 = 201