Put all the white balls in one box and the red ball in the other so you have a 50% chance of winning if you put 1 red ball and a white now you have a 25% chance cause you have a 50% chance in choosing the right box then you have to chose the right ball which would be 50%
You get 4/10 because there are 10 rows and 10 columns. 10*10 is 100. 40 0f them are shaded so it would be 40/100. You need to simplify by dividing by 10 and you get 4/10.
