Problem with ratios?

Answer is 141:423, so the ones who didn't want the main course is 423.

1] Add the two ratio numbers together for 4.

2] Divide the number of total students, 564 by this total of 4.

3] 141, which then is multiplied across the ratio of 1:3.

4] 141x1:141x3.

5] 141x423. Which equals 564, the kids in the lunchroom.

I'm sure someone can lay out a good formula for you, but that's the process for your problem.

Write your ratio as a fraction. The ration 1:3 becomes the fraction

...1

------ which means the number of people who eat the main course is 1 and the

...3............................number of people who don't eat the main course is 3;

.................................notice that in this fraction there are a total of 1+3=4 people

Now change the last statement into a fraction with x being your unknown quantity:

" If 564 kids are in the lunchroom each day, how many don't eat they main course?"

becomes the fraction

.....x

---------- which means the number of people who eat the main course is x, and

564-x.......................the number of people who don't eat the main course is (564-x).

...............................notice that in this fraction there are a total of x+(564-x)=564 people.

You need to solve for the number of people who don't eat the main course. In other words,

solve for (564-x).

To do this, set the 2 fractions equal to each other. You can do this because the simply

represent proportions.

....1..........x

-------- = -----------

....3.......(564-x)

Now cross multiply and solve for x. When you've done that, solve for (564-x).

3x = 1(564-x)

3x = 564 - x

4x = 564

x = 564/4

x = 141

(564-x) = 564-141 = 423.........There are 423 people who DON'T eat the main course.......ANS

se il rapporto non è 1/3 rimane di essere 2/3,,,,,allora 564/2*3=282*3=846 bambini che non mangiano.