In a class of 100
80 have atleast one pen
65 have atleast one pencil
70 have atleast one slate
If a is max no of classmates having all three
and b min no of classmates having all three,
Calculating a is straightforward. But I fail to understand the logic behind calculating b. Can someone please explain the logic behind calc. b? I know the answer. Thanks.
I make it C?
The min number of people with both Pens and Pencils will be 50 - There are twenty people who don't have a pencil - if all of those have a pen, then there will be 50 left who have to have a pen.
Thus there will be 50 with both, and 50 with one or the other. As to the slate then, up to 50 people can have either the slate and the pen, or the slate and the pencil, but not all three. Thus there are 15 people at minimum who must fall into all three.
I think that makes sense!