Abookshop has a sale.
a book normally costing $39.95 is priced at $23.97.
by what percentage has the price been reduced?

show working out

The price been reduced by a percentage of 40%

Step-by-step explanation:

we know that

$39.95 > represent the 100%

so

The difference of prices is equal to ($39.95-$23.97)=$15.98

Using proportion

Find the percentage of the difference

100/39.95=x/15.98

x=100*15.98/39.95

x=40%

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional