21 Divided by What Equals 55?
Methods
Setting up the problem:
In a problem like this, the “what” means that we’re working with a variable. The most common variable used in math is “x”. So we could say what number, x can we divide 21 by to equal 55?
Solving 21 Divided by What Equals 55
Here’s how you would set up this question as an equation:
21
x
=
55
\frac{21}{x} = 55
x 21 = 55
The goal of the problem is to solve for x. To do this we need to change the equation so that x is alone on one side of the equation.In this case, it can be done in two steps. The first step is to multiply both sides by x to isolate 21:
21
=
55
∗
x
21 = 55*x
21 = 55 ∗ x
Then we can isolate x on the right side of the equation by dividing both sides by 55:
21
55
=
x
\frac{21}{55} = x
55 21 = x
When we simplify the new equation, we can solve for x. In this example, we will round to the nearest three decimal places if that’s needed.
x
=
0.382
x = 0.382
x = 0.382
Practice Other Division Problems Like This One
If this problem was a little difficult or you want to practice your skills on another one, give it a go on any one of these too!
What divided by 39 equals 40?
11 divided by what equals 36?
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What is 66 divided by 1/18?