India and South Africa play One Day International Series until one team wins 4 matches. No match ends in a draw. Find in how many ways series can be won ?

Explanation

Taking I for india and S for south africa. We can arrange I and S to show the wins for india and south africa,
respectively.
for example, ISSSS means first match is won by india which is followed by 4 wins by south africa. This is onw way in which series can be won.
suppose, south africa wins the series, then last match is always won by south africa.

`therefore`Total number of ways=35
In the same numbe of ways, india can win the seires.
`therefore`Total number of ways in which the series can be won
`=35xx2=70`