hiiiii

 

The answer is correct ..... read the question once again ...

 

Well the question says that ... either a boy or a girl who knows cricket

 

You have misinterpreted it ... (a boy) or (girl who knows cricket)

 

So there are 60 boys and half out of 20 girls know cricket .. rite ..

 

So we can chooose from 60+10 persons ...

 

Thus the probability is 70/80 (since 80 is the size of total space)

 

Thus answer is 7/8

 

I hope u have got my point ....

 

cheers