Please someone help

[F1_kenzo]

Can somebody please explain to me the method to work out this equation,

5 x .8 : 7.2 what does x equal.
Thanks

 

[JeffM]

To start with, what you have shown is not an equation. Please give us the complete and exact wording of the problem as we request in our guidelines. It would also help if you tell us what you are studying.

 

[F1_kenzo]

Sorry the correct equation is

5x :8 = 7.2

what is x

it is a ratio equation my year 10 teacher gave me to find the method of how to work it out.

 

[Dr.Peterson]

Sorry the correct equation is

5x :8 = 7.2

what is x

it is a ratio equation my year 10 teacher gave me to find the method of how to work it out.

Are you using ":" to mean division? If so, then the equation can be written as [MATH]\frac{5x}{8} = 7.2[/MATH]. A ratio is essentially the same thing; but we don't tend to write equations like this, setting a ratio equal to a number.

To solve this, I would first multiply both sides by 8, then divide by 5, in order to isolate x.

What have you tried?

 

[F1_kenzo]

Are you using ":" to mean division? If so, then the equation can be written as [MATH]\frac{5x}{8} = 7.2[/MATH]. A ratio is essentially the same thing; but we don't tend to write equations like this, setting a ratio equal to a number.

To solve this, I would first multiply both sides by 8, then divide by 5, in order to isolate x.

What have you tried?

 

[F1_kenzo]

T
this is the working out my teacher gave me but I do not understand it can u explain it too me if possible

 

[JeffM]

If that is your teacher's explanation, your teacher should be fired (executed might be more appropriate).

The notation is sloppy, and the explanation meaningless because it does not say where the 28 came from.

[MATH]5x \ : \ 8 \ :: \ 7 \ : 2 \text { MEANS } \dfrac{5x}{8} = \dfrac{7}{2}.\\ \therefore 8 * \dfrac{5x}{8} = 8 * \dfrac{7}{2} \implies 5x = 28 \implies x = \dfrac{28}{5}.[/MATH]Does that make sense to you? So we can replace x with 28/5.

[MATH]5 * \dfrac{28}{5} \ : \ 8 \ :: \ 7 \ : \ 2.[/MATH]
The whole point of ratios is to explain things in terms of whole numbers so why an example using improper fractions is used is beyond me.

(By the way, this is not advanced math.)

 

[Dr.Peterson]

I see that even when you corrected your statement of the problem to 5x :8 = 7.2 in post #3, you got it wrong.

It is extremely important to play close attention to details when you work on a math problem.

 

[Steven G]

7:2 is the same as 7*4:2*4 or 28:8
I multiplied by 4 in order to get 8 as in 5x:8

In order for 5x:8 = 28:8 we need 5x = 28 or x = 28/5 .................................edited

Thank you,