31% of ? = 17.2: Percentage of 31 (percent) calculated of what missing unknown number equals the given value, 17.2?
31% of what missing number = 17.2?
Detailed calculations and the verification of the result
A brief introduction. Percent, p%
'Percent (%)' means 'out of one hundred':
31% = 31 'out of one hundred',
p% is read p 'percent',
p% = p/100 = p ÷ 100
31% = 31/100 = 31 ÷ 100 = 0.31
100% = 100/100 = 100 ÷ 100 = 1
What does it mean: Percentage of 31% of which number is equal to 17.2?
31% of what number = 17.2
... is equivalent to multiplying them:
31% × number = 17.2
Number calculation, finding the missing unknown number
Percentage of 31% of what number = 17.2?
Let y be the number that we have to calculate.
31% × y = 17.2 =>
y =
17.2 ÷ 31% =
17.2 ÷ (31 ÷ 100) =
(100 × 17.2) ÷ 31 =
1,720 ÷ 31 ≈
55.483870967742 ≈
55.48
31% of 55.48 ≈ 17.2
Proof of the calculations
How do we check the result?
We carry out the reverse operation:
If 31% × 55.483870967742 = 17.2 =>
Divide the number 17.2 by the number 55.483870967742...
... And see if we get as a result: 31%
A quick note:
Multiply a number by the fraction 100/100, ... and its value doesn't change.
100/100 = 100 ÷ 100 = 1
By multiplying a number by the fraction 100/100, we change only the form of the result, not the result.
n/100 = n%, any number.
Calculate the percentage value: See if we get the percentage of 31%
We will prove below that the calculations are correct.
17.2 ÷ 55.483870967742 ≈
0.31 =
0.31 × 100/100 =
(0.31 × 100)/100 =
31/100 =
31%
So, we have proven that the calculations were correct. The answer (scroll down)... :: written in two ways ::
Percentage of 31% of what number = 17.2? 31% × ? = 17.2
Rounded off to a maximum of 12 decimal places: 31% of 55.483870967742 ≈ 17.2
Rounded off to a maximum of 2 decimal places: 31% of 55.48 ≈ 17.2
The symbols used: % percent, ÷ division, × multiplication, = the equal sign, / the fraction bar, ≈ approximately the same. Writing numbers: comma ',' - as a thousands separator, point '.' as a decimal mark.
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Three examples of problems that can be solved out using the information in this section:
Problem 1:
25% of the annual profit of a company was invested in buying some new equipment. The total amount invested in buying the new equipment was 100,000 dollars. What was the annual profit of the company?
A number of 20% of the students in the terminal year have enrolled into the swimming class. In total, 7 students have enrolled. How many students are in the terminal year?
Rewrite: 20% of the students means 7 students => 20% × Total number of students = 7 => The total number of students = 7 ÷ 20% = 7 ÷ 20/100 = 7 × 100/20 = 7 × 5 = 35;
Problem 3:
In the last elections 49% of community memebrs voted for the A Party, 32% for the B Party, and the rest for the C Party. 17,920 people voted for the B Party. How many members are in the community, all in all?
Rewrite: 32% of the total community members means 17,920 people => 32% × The total number of community members = 17,920 => The total number of community members = 17,920 ÷ 32% people = 17,920 ÷ 32/100 people = 17,920 × 100/32 people = 17,920/32 × 100 = 560 × 100 people = 56,000 people.