This worksheet is about keeping pairs of numbers in the same ratio.
If two quantities are in direct proportion, the ratio between corresponding values will always be the same.
a  =  1  2  3  4  5 
b  =  1.5  3  4.5  6  7.5 
1.5  3  4.5  
=  =  
1  2  3 
b is directly proportional to a.
Here b = 1.5 x a
To find b when a = 6, we solve 

= 

b = 6 × 1.5 = 9 
To find a when b = 12, we solve 

= 

a = 12 ÷ 1.5 = 8 