Question

If x varies as y and if x=20 when y=9 , find x when y=18​

Answer 1

Answer:1/2 y

Step-by-step explanation:

We can solve this using ration reasoning:  

x

2

x

1

=

y

2

y

1

Explanation:

If  

x

varies directly with  

y

(written  

x

∝

y

), then doubling  

y

means doubling  

x

, so the rations of final values and initial values will be the same:

x

2

x

1

=

y

2

y

1

In this case,

x

2

9

=

24

18

x

2

=

9

⋅

24

18

=

12

Or, intuitively, if  

x

∝

y

and  

x

=

9

when  

y

=

18

, we can conclude that

x

=

1

2

y

and  

1

2

of 24 is 12.