87 Divided by What Equals 21?
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 87 by to equal 21?
Solving 87 Divided by What Equals 21
Here’s how you would set up this question as an equation:
87
x
=
21
\frac{87}{x} = 21
x 87 = 21
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 87:
87
=
21
∗
x
87 = 21*x
87 = 21 ∗ x
Then we can isolate x on the right side of the equation by dividing both sides by 21:
87
21
=
x
\frac{87}{21} = x
21 87 = 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
=
4.143
x = 4.143
x = 4.143
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 95 equals 98?
80 divided by what equals 4?
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What is 4/2 divided by 12/17?
What is 11 divided by 10/9?