Question
1) There are 20 balls which are red,blue or green.If 7 balls are green & the sum of red balls & green balls is less than 13,atmost how many red balls are there?
2)A drawer holds 4 red hats & 4 blue hats.what is the probability of getting exactly three red hats or exactly three lue hats when taking out 4 hats randomly out of the drqwer & immediately returning every hat to the drawer before taking out the next?
3)In how many ways can we distribute 10 identical looking pencils to 4 students so that each students gets at least one pencil?
4)Mr &mrs smith have invited 9 of their friends & their spouses for a party at the waikki beach resort.they started for a group photograph.if Mr.smith never stands next to mrs smith(as he says they are always together otherwise).how many ways the group can be arranged in a row for the photograph?