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If x and r are directly proportional and x = 5 when r = 25, then what is x when r = 40?

 Apr 19, 2021
 #1
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I'm pretty sure the answer is 8, because when r = 25 and x = 5, you have to divide r by 5 to get x. This way, because 40/5 is 8, I think that would be the answer you're looking for.

 

 

So x = 8.

 Apr 19, 2021
edited by Guest  Apr 19, 2021
 #3
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Im asking for x...

Guest Apr 19, 2021
 #5
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Lol I'm so sorry, I meant x = 8, not r = 8. I fixed it in the post now :)

Guest Apr 19, 2021
 #6
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Ok thx it's correct :)

Guest Apr 19, 2021
 #2
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x and r are directly proportional means we can write;  x = k*r where k is a constant.

 

To find k use the fact that x = 5 when r = 25, so   5 = k*25 .  You should be able to find k from this.

 

Then use that to find x when r is 40:  x = k*40

 Apr 19, 2021
 #4
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SO x = 8?

Guest Apr 19, 2021
 #7
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If x and r are directly proportional and x = 5 when r = 25, then what is x when r = 40?

 

x : r = 5 : 25

 

5 : 25 = x : 40

 

x = (5 * 40) / 25

 

x = 8

 Apr 19, 2021

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