21 is 70% of what number?
Understand the Problem
The question is asking what number corresponds to 21 being 70% of it. This is a straightforward mathematical problem that involves finding an unknown in a percentage equation.
Answer
$30$
Answer for screen readers
The unknown number is $30$.
Steps to Solve
- Set up the equation
Let the unknown number be represented as $x$. The problem states that 21 is 70% of $x$. We can express this relationship as an equation: $$ 0.7x = 21 $$
- Isolate the unknown
To find the value of $x$, we need to isolate it on one side of the equation. We can do this by dividing both sides by 0.7: $$ x = \frac{21}{0.7} $$
- Calculate the result
Now, let’s calculate the value: $$ x = 30 $$
The unknown number is $30$.
More Information
When 21 is 70% of another number, that number is 30. This is an example of using a percentage to find a whole value.
Tips
One common mistake is multiplying 21 by 0.7 instead of using division. Remember that to find the whole when given a part and a percentage, you divide the part by the percentage (expressed as a decimal).
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