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If x and y vary directly, and x = 12 when y = 3, what will be the value of x when y = 9?

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If you think about it, x=12 when y=3, right?
So the function is going to be f(x)=y*4
So, if y = 9 and you put it in the function, x is going to equal 36.
Do this help you understand?

User Florian Salihovic
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Answer: The required value of x is 36.

Step-by-step explanation: Given that the variables x and y varies directly. Also, x = 12 when y = 3.

We are to find the value of x when y = 9.

Given that x and y varies directly. So, we have


x\propto y\\\\\Rightarrow x=k~y,~~~~~~~~~~~~~~~~~~~~(i)

where 'k' is the constant of proportionality.

Given that x = 12 when y = 3, so from equation (i), we have


x=k~y\\\\\Rightarrow 12=k* 3\\\\\Rightarrow k=(12)/(3)\\\\\Rightarrow k=4.

Substituting the value of k in equation (i), we have


x=4y~~~~~~~~~~~~~~~~~~~~(ii)

When y = 9, we get from equation (ii) that


x=4* 9\\\\\Rightarrow x=36.

Thus, the required value of x is 36.

User MaVVamaldo
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