how to set up: How many trays contain both cup and plate?

[Love21]

There are 25 trays on a table in the cafeteria. Each tray contains a cup only, a plate only or both a cup and a plate. if 15 of the trays contain cups and 21 of the trays contain plates, how many contain both a cup and a plate?

15 trays = have cups
21 trays = have plates
=25 trays total

hm have cup and plate?

HOW would you figure this out?? Help is needed.
Thanks !!

 

[Loren]

Re: advanced word problem-how to set up

Think about how many trays don't have plates and how many trays don't have cups leaving you with how many trays have only one item. That should tell you haw many trays have both items.

 

[Deleted member 4993]

There are 25 trays on a table in the cafeteria. Each tray contains a cup only, a plate only or both a cup and a plate. if 15 of the trays contain cups and 21 of the trays contain plates, how many contain both a cup and a plate?

15 trays = have cups
21 trays = have plates
=25 trays total

hm have cup and plate?

HOW would you figure this out?? Help is needed.
Thanks !!

Use a Venn diagram to solve this problem.