Let’s Find the Missing Number in the Series 3 8 18 38 78 ??

Here in this series, we can see that value of numbers is increasing.

Suppose our last number is X.

Then our complete series will be 3, 8, 18, 38, 78, X.

Now we will find the difference of two consecutive terms by subtracting the first term from the second term in all series.

8 – 3 = 5

18 – 8 = 10

38 – 18 = 20

78 – 38 = 40

X – 78 = ??

Now we get a simplified series

5, 10, 20, 40, ?

5*1, 5*2, 5*4, 5*8, 5*16 as per the series

So our next difference will be 5*16 = 80

Hence our next series terms will be

X – 78 = 80

X = 80 + 78

X = 158

Hence our complete series will be 3, 8, 18, 38, 78, 158.

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