Posted by Kendra on Monday, August 10, 2009 at 5:45pm.
A pollster interviewed 500 university seniors who owned credit cards. She reported that 240 had Goldcard, 290 had Supercard, and 270 had Thriftcard.
Of those seniors, the report said that:
80 owned only a Goldcard and a Supercard,
70 owned only a Goldcard and a Thriftcard,
60 owned only a Supercard and a Thriftcard, and
50 owned all three cards.
When the report was submitted for publication in the local campus newspaper, the editor refused to publish it, claiming the poll was not accurate. Was the editor right? Why or why not?

word problem Math  Ms. Sue, Monday, August 10, 2009 at 6:38pm
The editor was right. The numbers add up to more than 500.

word problem Math  Reiny, Monday, August 10, 2009 at 8:02pm
Using the formula ...
n(A or B or C)
= n(A) + n(B) + n(C)  n(A and B)  n(A and C)  n(B and C) + n(A and B and C)
500 = 240 + 290 + 270  80  70  60 + 50
500 = 640
not true, so data not consistent.
You could also make Venn diagrams to show the data distribution.