Because out of two possibilities we can have either a boy or girl. And so each one of those possibilities is equally likely and so they are given 50%. So we have a half and a half which are equivalent to 50%. So now let's actually create the Punnett square. So we combine B, red B, we have the second event or a blue B, a red B and a purple B. So we have a B, then we have the red B boy and we have the third one.