let x be number of balls ordered of either color.

6/5= x+30/x
6x=5x + 150
x= 150

total order is 2x = 300 (since equal number of both colors ordered)

Can you tell me why you have the /x on the right hand of the equation??


I get why its 6/5 = x+30 but why x+30/x???

If it helps, here's how i thought of it.

They intended to order an equal amount of each color, a 1:1 ratio. a 5:5 ratio = 1:1.

Since 30 extra balls made the ratio 6:5, then 30 equals 1/5th of the intended order for each color. So 5*30 + 5*30 = 300.

Adding onto elmiko,

I actually did this question without picking up the pen.

This is what I did, the question is saying that that the ratio of the balls was 6:5.

I instantly realized that 6/11 of X number must be equal to white balls.

Now we know the balls cant be 1/2 or 3/4 of a ball. So I quickly scanned the list and there was only choice which multiplied with 6/11 cleanly. 330. Now i remembered we added 30 so I subtracted that and I got 300. Sometimes its good when the examiners try to trick us with tempting answers.

Did I over-simplify this?

Sumi

I think the most academic and simple way (without shortcuts of any sorts) is

W/Y = 1/1
&
(W+30)/Y=6/5

Simplification of first ratio gives: W = Y

Simplification of 2nd: 5(W+30) = 6Y therefore 5W + 150 = 6Y

Finally, as Y=X we have 5W + 150 = 6W

W= 150 therefore Y = 150 therefore total of W + Y = 300

I do not know but it seems clearer to me to think about it as a system of equation...

JB

Let x be the white
Let y be the yellow

x/y = 1/1 i.e x=y

When u add 30

x+30/y = 6/5
5x+150 = 6y

5y+150 = 6y ( x=y)

y=150 x=150 D)