You have to closely watch the series, since the series if increasing quickly you get a hint that an exponential component would be present.
The connection between the numbers in the series is as described below;
So we can fit this into the numbers and see if it’s correct.
If you notice all the equations the result is the product of the given number and double that number.
2 x 4 = 8
3 x 6 = 18
4 x 8 = 32
5 x 10 = 50
? = 10 x 20 = 200