The following rectangular arrays of dots suggests a sequence

The following rectangular arrays of dots suggests a sequence of number:

* * * * *

* * * * * * * * *

* * * * * * * * * * * *

* * * * * * * * * * * * * *

(2) (6) (12) (20)

(a) How many dots will there be in the next array?

(b) How many dots will there be in the 100th array?

In the first array There are 1 row and 2 columns resulting in 1*2=2 dots

In the second array There are 2 row and 3 columns resulting in 2*3=6 dots

In the third array There are 3 row and 4 columns resulting in 3*4=12 dots

In the fourth array There are 4 row and 5 columns resulting in 4*5=20 dots

In the next array ie., The fith array will consist of 5 rows and 6 columns resulting in 5*6=30 dots

In the 100^th array There will be 100 row and 101 columns resulting in 100*101=10100 dots

In the n^th array There will be n row and (n+1) columns resulting in n*(n+1)=n(n+1) dots