in a bag there are 20 red 30black 40 blue50 white balls. what is the minimum number of balls to be drawn without replacement so that you are certsin about getting 4 red,5 black,6 blue,7 white balls

Answer 1

Red is the hardest to get, since there are only 20 of them.
To make sure you get some red, the worst case is you picked all the black, blue and whites (totalling 120) and still not get a red.
What is the minimum you need?