find x     10:1=20:x

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pohnpei397's profile pic

pohnpei397 | College Teacher | (Level 3) Distinguished Educator

Posted on

While the above answer is, of course, correct, I'd like to explain how to get the answer in hopes that an explanation might help you do other problems like this on your own.

What you're being asked here is essentially this equation:


The most usual way to find for x when you have an equation like this is to cross-multiply.  That is, you multiply the top of one fraction by the bottom of the other.

That gets you 10X=20

You then divide both sides by 10 and you get x=20

You can use this technique whenever you need to solve for x in a fraction like this.

malkaam's profile pic

malkaam | Student, Undergraduate | (Level 1) Valedictorian

Posted on


You can solve this by looking at it, as you can see that 10 : 1, and when the amount is doubled and becomes 20 x also doubles and becomes 2. Since ratio can also be expressed as a fraction you can also do it like this:

10/1 = 20/x

10x = 20/x * x            (multiply both sides by x)

10x = 20

10x/10 = 20/10            (divide both sides by 10)                               

x = 2 Answer

atyourservice's profile pic

atyourservice | Student, Grade 11 | (Level 3) Valedictorian

Posted on


Just put it as a fraction and cross multiply

`10/1= 20/x  `

20 = 10x

divide by 10

`20/10 = (10x)/10 `

2 = x

so x is 2

jess1999's profile pic

jess1999 | Student, Grade 9 | (Level 1) Valedictorian

Posted on


Basically 10/1 = 20/x

First to solve this proportion, multiply 10 with " x " and 20 with 1

By multiplying , your equation should look like

10x = 20 now divide both sides by 10

By dividing, your equation should look like

x = 2 which is your answer

Wiggin42's profile pic

Wiggin42 | Student, Undergraduate | (Level 2) Valedictorian

Posted on

We need to find x .     10:1 = 20:x

This is a proportion and can also be written like this: 

10 / 1 = 20 / x 

We can cross multiply these fractions : 

10x = 20

Solve for x by dividing by 10. 

x = 2 

giorgiana1976's profile pic

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted on

Using the equivalent proportions we can notice the followings:



We've noticed that at numerator, we've multiplied it with 2, so in order to maintain the equality of proportions, we've concluded that  the unknown "x" is the result of the denominator of the left side ratio, multiplied also with 2. So the expression above could be written:

10:1=(10*2):(1*2), where the denominator from the right side (1*2)=x, so x=2

neela's profile pic

neela | High School Teacher | (Level 3) Valedictorian

Posted on

This is a problem on ratio and proportion.

We can do the problem  in  the usual ratio and proportion way itself. It is asked to find the fourth proportion.

Here the product of first and fourth term are equal to the product of middle terms. So, first term*fourth term = 10*x . The product of middle terms = 1*20. Therefore, 10x = 20 and solve for x.  So, x = 20/10 = 2.

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