2 Answers
John P
Nov 10, 2016
200
Explanation:
#40/x = 20/100#
#40/x*100 =20/100*100#
#4000/x = 20#
#4000*x/x =20*x#
#4000 = 20x#
#4000/20 = (20*x)/20#
#200 = x#
Answer link
Suren Abreu
Nov 10, 2016
#200#.
Explanation:
The equation can be expressed as:
#x xx20/100=40#
Multiply both sides by #100/20#.
#x=40xx100/20#
#x=4000/20#
#x=200#
Answer link
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- p% of A = ?
- p% of ? = A
- ?% of A = B
- fractions a/b = ?%
- relative change
- p% = ? number
- (1 + p%) × n
- (1 - p%) × n
40% of what missing number = 20?
Detailed calculations and the verification of the result
A brief introduction. Percent, p%
'Percent (%)' means 'out of one hundred':
40% = 40 'out of one hundred',
p% is read p 'percent',
p% = p/100 = p ÷ 100
40% = 40/100 = 40 ÷ 100 = 0.4
100% = 100/100 = 100 ÷ 100 = 1
What does it mean:
Percentage of 40% of
which number is equal to 20?
40% of what number = 20
... is equivalent to multiplying them:
40% × number = 20
Number calculation, finding the missing unknown number
Percentage of 40% of what number = 20?
Let y be the number that we have to calculate.
40% × y = 20 =>
y =
20 ÷ 40% =
20 ÷ (40 ÷ 100) =
(100 × 20) ÷ 40 =
2,000 ÷ 40 =
50
40% of 50 = 20
Proof of the calculations
How do we check the result?
We carry out the reverse operation:
If 40% × 50 = 20 =>
Divide 20 by 50...
... And see if we get as a result: 40%
A quick note:
Multiply a number by the fraction 100/100,
... and its value doesn't change.
100/100 = 100 ÷ 100 = 1
n/100 = n%, any number.
Calculate the percentage value:
See if we get the percentage of 40%
We will prove below that the calculations are correct.
20 ÷ 50 =
0.4 =
0.4 × 100/100 =
(0.4 × 100)/100 =
40/100 =
40%
The answer:
Percentage
of 40% of what number = 20?
40% × ? = 20
40% of 50 = 20
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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- p% of what missing number = the given number N?
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?
- Rewrite: 25% of the Profit means 100,000 dollars => 25% × Profit = 100,000 dollars => Profit = 100,000 ÷ 25% dollars = 100,000 ÷ 25/100 dollars = 100,000 × 100/25 dollars = 100,000 × 4 dollars = 400,000 dollars;
Problem 2:
- 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.