[size=100][size=150][color=#0000ff]Per cent[/color] means  one of a hundred and it comes from latin ([i]per centum, pro centum[/i]). [br][br] [math]\huge \textcolor{blue}{1 \text{ per cent}=1\%=\frac{1}{100}=0.01.}[/math][br] [br]It is very much used in every field of life: loans, taxes, sales etc. Without undestanding its meaning, one's life can be very difficult. [br] [br]The formula for percentage is [br][br] [math]\huge \textcolor{blue}{p=\frac{b}{a}\;\;\;\text{or}\;\;\;p=\frac{100b}{a}\%,}[/math][br] [br]where [i][color=#0000ff]b[/color][/i][color=#0000ff] "=" [/color][i][color=#0000ff]p[/color][/i][color=#0000ff] but in units [/color](like kg, euro,  etc.) and [i][color=#0000ff]a[/color][/i][color=#0000ff]  is the basic value [/color](original value, quantity of mixture).  [/size][/size]

There are 12500 people working in marketing and sales in an international company. The total number of workers in the company is 21630. How many per cents of workers are in marketing and sales?[br][br]In this case, [i]p [/i]is asked. As [i]b[/i] refers to same as [i]p[/i] but only in units, then [i]b[/i] = 12500. The basic value [i]a[/i] = 21630.[br][br] [math]\Large p=\frac{b}{a}=\frac{12500}{21630}=0.578=57.8\%[/math]

The label of a wine bottle of 750 ml informs that the percentage of alcohol is 13%. How much pure alcohol is there in the bottle?[br][br]The basic value is the volume of the bottle, so [i]a[/i] = 750 ml. The percentage of alcohol is 13%, so [i]p [/i]= 0.13. As [i]b[/i] is the amount of pure alcohol, then[br][br][math]\Large b=pa=0.13\cdot 750\text{ ml}=97.5\text{ ml}.[/math]

A carpet is in sale. The price of the carpet is 39 euros and it is said that price is decreased by 43%. What was the original price of this carpet?[br][br]As the price is decreased by 43%, the new price is 100% - 43% = 57% of the original price. Thus, [i]p[/i] = 57% and [i]b[/i] = 39 euros. The basic value is asked, so[br][br][math]\Large a=\frac{b}{p}=\frac{39\text{ euros}}{0.57}= 68.42\text{ euros}\approx 68\text{ euros}[/math]

A drink called [i]Kelkka[/i] consists of [br][br]2 cl Absolut Kurant[br]2 cl Passoã Passion Fruit[br]10 cl Orange juice.[br][br]What is the percentage in alcohol for this drink?[br][br]Absolut Kurant has 40% of alcohol and Passoã Passion Fruit has 17% of alcohol. Thus, there is pure alcohol in the drink[br][br][math]\Large b=\;0.40\cdot 2\text{ cl }+ 0.17\cdot 2\text{ cl } = 1.14 \text{ cl.}[/math][br][br]The total amount of the drink is [math]\Large a=\; 2\text{ cl } + 2\text{ cl }+ 10\text{ cl }= 14\text{ cl.}[/math][br][br]So, the percentage in alcohol is [br][br][math]\Large p=\frac{b}{a}=\frac{1.14\text{ cl}}{ 14\text{ cl}}=0.081 \approx 8\%.[/math][br]