Question

when X varies directly as to 2y.

find X= 1 and Y = 20 find Y when x = 9

Answer 1

x proportional to 2y

Therefore,

x = c (2y)
where c is the proportional constant.

Given that x = 1 when y = 20

So,
x = c (2y)
1 = c (2)(20)
1 = c (40)
c = 1/40

Now for x = 9,

x = c (2y)
9 = (1/40)(2y)
9 = (1/20)y
y = 180.

Answer 2

Answer: y = 180

Step-by-step explanation:

according to the question we have to understand that

the ratio is 1 : 40(if y = 20 then 2y = 40)

where x is 1

and 2y = 40

so if x was 9

then 2y should be 9 * 40 ( we are doing this so that the ratio remains same)

=> 2y = 360

=> y = 360 / 2 = 180