## Katieann16 2 years ago y varies directly with x, and y = 2 when x = 5. What is the value of x when y = 15?

1. Katieann16

@jim_thompson5910

2. jim_thompson5910

y varies directly with x so this means y = kx where k is some fixed number

3. jim_thompson5910

we are told that y = 2 when x = 5 so y = kx 2 = k*5 solve for k

4. Katieann16

so 6?

5. jim_thompson5910

when you solved for k, what did you get

6. Katieann16

wait how do i solve for k

7. jim_thompson5910

2 = k*5 divide both sides by 5 to isolate k

8. jim_thompson5910

k = ???

9. Katieann16

2.5?

10. jim_thompson5910

you divided in the wrong order

11. Katieann16

0.4?

12. jim_thompson5910

good, so y = kx turns into y = 0.4x

13. jim_thompson5910

now you want to find x when y = 15, so y = 0.4x 15 = 0.4x now solve for x

14. Katieann16

37.5?

15. jim_thompson5910

you nailed it you can also represent 37.5 as the fraction 75/2

16. jim_thompson5910

so x = 37.5 or x = 75/2

17. Katieann16

ok thank you(:

18. jim_thompson5910

you're welcome