Of the science books in a certain supply room, 50 are on botany, 65 are on zoology, 90 are on physics. 50 are on geology, and 110 are on chemistry. If science books are removed randomly from the supply room, how many must be removed to ensure that 80 of the books removed are on the same science?
Can someone please explain this....
To ensure you remove 80 of the same, you need to assume the worst case scenario. That is you first remove the 50 botany, 65 soology, 50 geology. You now have 165 and you don't have 80 of the same.
Then you remove another 79 of one (either physics or chemistry). Lastly you take out another 80 and then you are sure you have 80 of the same.
Add them all up and you get 324.