# Either Courses

• Oct 2nd 2008, 05:24 AM
magentarita
Either Courses
In a class of 450 students, 300 are taking a mathematics course and 260 are taking a science course. If 140 of these students are taking both courses, how many students are not taking either of these courses?
(1) 30 (3) 110
(2) 40 (4) 140

I know there is a formula or equation for "EITHER" questions such as this one.

What is a good formula or equation to use to find the answer?
• Oct 2nd 2008, 05:43 AM
mr fantastic
Quote:

Originally Posted by magentarita
In a class of 450 students, 300 are taking a mathematics course and 260 are taking a science course. If 140 of these students are taking both courses, how many students are not taking either of these courses?
(1) 30 (3) 110
(2) 40 (4) 140

I know there is a formula or equation for "EITHER" questions such as this one.

What is a good formula or equation to use to find the answer?

I'd suggest you draw a Venn diagram. From it, you should see that the number of students studying mathematics or science is 300 + 260 - 140 = 420 ....
• Oct 2nd 2008, 10:52 AM
kbartlett
A + B - (A and B) = (A or B)
Maths + Science - Both = Either
300 + 260 - 140 = 420
So 420 are taking either maths, science or both meaning that there are 30 students which are not taking either maths or science.
• Oct 2nd 2008, 02:42 PM
magentarita
yes...
Quote:

Originally Posted by mr fantastic
I'd suggest you draw a Venn diagram. From it, you should see that the number of students studying mathematics or science is 300 + 260 - 140 = 420 ....

Yes, but I know there is an equation given for such questions. I just can't think of it right now. At the end of the equation, there is a G_1 + G_2 to represent the two groups or something like that.

Do you know which equation it is?