White shapes and black shapes are used in a game. some shapes are circles. All the other shapes are squares.
The ratio of the number of white shapes to the number of black shapes is 5:11
The ratio of the number of white circles to the number of white squares is 3:7
The ratio of the number of black circles to the number of black squares is 3:8
work out what fraction of all the shapes are circles

The best way to approach this problem is to assign values that fit the ratios.

First we consider the ratio of white and black shapes. Since it's , let's assume that there are  white shapes and  black shapes.

Next we look at the ratio of white circles to white squares which is . This means that  of the white shapes are circle and  are square. This will lead us to have  white circles and  white squares.

Then, we look at the ratio of black circles to black squares (). We can get at the number of black circles and black squares by performing the same step as before:

black circles

black squares

Now that we have all the assumed values, we just proceed to get the fraction of circles by counting the assumed number of circles and dividing it by the total number of assumed shapes. (We can get the total number of assumed shapes by adding the number of black and white shapes).

ANSWER:  of all shapes are circles.

(This method will work since we have maintained the given ratios.)

distance covered by pamela in 9 l of fuel = 99km

let us apply unitary method here.

distance covered by pamela in 1 l of fuel =99/9 =11 km

now let us find distance covered by pamela if she has 12 l of fuel.

distance covered in 12 l = distance covered in 1 l of fuel * 12

we know that distance covered by here in 1 l is 11 km.

so distance covered in 12 l of fuel = 11*12 = 132 km.