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:

10/1=20/x

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.

10:1=20:x

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**

10:1=20:x

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

10:1=20:x

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

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

Using the equivalent proportions we can notice the followings:

10:1=20:x

10:1=(10*2):x

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**

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.