I have a math question please help?

Question

Four-fifths of Mrs. Burrow's clas likes the color purple, while 7/8 of ms. chen's class likes the color....
what fraction of both classes like purple?
do i mutiply or add? or what?

Answer 1

Data insufficient to find answer.
Let me illustrate:
Suppose 40 people study in both Mrs. Burrow's and Chen's class
The total purple loving people would be 4(8) + 7(5)
= 32 +35 = 67.
So fraction fo people who love purple is 67 /80

Suppose 40 people study in Mrs. Burrow's and 16 in Chen's class
The total purple loving people would be 4(8) + 2(7)
=32 + 14 = 46
So fraction fo people who love purple is 46 / 56 which is obviously not equal to 67 /80.
So the fraction can be anything depending on the number of people in each class.

You can understand this fact better using the concept of equation in 2 variables.
The given condition can be transformed as
(32x + 35y) / (40x + 40y)
This can take any Real value and youll get solutions.
{However meaningful solutions can be got using proper fractions}

Answer 2

4/5 is the same as 32/40
7/8 is the same as 35/40

(35 + 32)/2 = 33.5

33.5/40 of both classes like purple
or 67/80

Answer 3

4/5=32/40
+ 7/8=35/40
_________
67/40=1 27/40