We already have our first value **21** and the second value **75**. Let's assume the unknown value is **Y** which answer we will find out.

As we have all the required values we need, Now we can put them in a simple mathematical formula as below:

STEP 1 21 = 75% × Y

STEP 2 21 = 75100× Y

Multiplying both sides by 100 and dividing both sides of the equation by 75 we will arrive at:

STEP 3 Y = 21 × 10075

STEP 4 Y = 21 × 100 ÷ 75

STEP 5 Y = 28

Finally, we have found the value of Y which is 28 and that is our answer.

You can easily calculate **21 is 75 percent of what number** by using any regular calculator, simply enter **21 × 100 ÷ 75** and you will get your answer which is **28**

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Here is a Percentage Calculator to solve similar calculations such as 21 is 75 percent of what number. You can solve this type of calculation with your values by entering them into the calculator's fields, and click *'Calculate'* to get the result and explanation.

**Question:** Your friend has a bag of marbles, and he tells you that 75 percent of the marbles are red. If there are 21 red marbles. How many marbles does he have altogether?

**Answer:** 28 marbles.

**How To:** In this problem, we know that the Percent is 75, and we are also told that the Part of the marbles is red, so we know that the Part is 21.

So, that means that it must be the Total that's missing. Here is the way to figure out what the Total is:

PartTotal = Percent100

By using a simple algebra we can re-arrange our Percent equation like this:

Part × 100Percent = Total

If we take the "Part" and multiply it by 100, and then we divide that by the "Percent", we will get the "Total".

Let's try it out on our problem about the marbles, that's very simple and it's just two steps! We know that the "Part" (red marbles) is 21.

So step one is to just multiply that Part by 100.

21 × 100 = 2100

In step two, we take that 2100 and divide it by the "Percent", which we are told is 75.

So, 2100 divided by 75 = 28

And that means that the total number of marbles is 28.

**Question:** A high school marching band has 21 flute players, If 75 percent of the band members play the flute, then how many members are in the band?

**Answer:** There are 28 members in the band.

**How To:** The smaller "Part" in this problem is 21 since there are 21 flute players and we are told that they make up 75 percent of the band, so the "Percent" is 75.

Again, it's the "Total" that's missing here, and to find it, we just need to follow our 2 step procedure as the previous problem.

For step one, we multiply the "Part" by 100.

21 × 100 = 2100

For step two, we divide that 2100 by the "Percent", which is 75.

2100 divided by 75 equals 28

That means that the total number of band members is 28.

Let's assume the unknown value is **Y**

First writing it as: **100% / Y = 75% / 21**

Drop the percentage marks to simplify your calculations: **100 / Y = 75 / 21**

Multiply both sides by Y to move Y on the right side of the equation: **100 = ( 75 / 21 ) Y**

Simplifying the right side, we get: **100 = 75 Y**

Dividing both sides of the equation by 75, we will arrive at **28 = Y**

This leaves us with our final answer: **21 is 75 percent of 28**

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