The percentage is a way of representing a fraction in which a total is divided into one hundred parts. For example, saying that an object contains 30% fat, means that if we divided it into 100 parts, 30 of them would be fat.
The % symbol It is equivalent in mathematics to the fact 0.01 that is to say that 1% is equal to 0.01.
A fraction is a relationship between two quantities. The percentage allows you to compare different amounts with respect to a total.
To find out the percentage of the total (Y) which represents a quantity X, we must divide X by Y, and then multiply it by 100.
For example, if the total of a food is 40 grams and it contains 15 grams of fat:
- 15/40 x 100 = 37.5%. That is, the food contains 37.5% fat.
To find out what a real quantity represents a percentage P of a total Y, multiply P by the total Y, and then divide it by 100. For example, if you want to know how much 30% of 120 is:
- 30 x 120/100 = 36. That is, 30% of 120 is 36.
A high percentage may indicate a real small amount. For example, if 90% of a tablespoon is sugar, it may be only 1.8 grams of sugar. While 15% of a packet of sugar can be 150 grams. Therefore, to know the actual quantity it is necessary to know with respect to what total quantity the percentage is measured.
Examples of percentages
- A fraction of 1/1 is 100%
- A fraction of 9/10 is 90%
- A fraction of 4/5 is 80%
- A fraction of ¾ is 75%
- A fraction of 7/10 is 70%
- A fraction of 3/5 is 60%
- A fraction of 1/2 is 50%
- A fraction of 2/5 is 40%
- A fraction of 3/10 is 30%
- A fraction of 1/4 is 25%
- A fraction of 3/20 is 15%
- A fraction of 1/8 is 12.5%
- A fraction of 1/10 is 10%
- A fraction of 1/20 is 5%
- A fraction of 1/50 is 2%
- A fraction of 1/100 is 1%
- A fraction of 1/200 is 0.5%
- In a group of 30 students, 12 are boys. 12/30 x 100 = 40. That is, 40% of the students are male.
- Veal is 20% fat, and a 300-gram serving is served at one meal. 20 x 300/100 = 60. This means that the food has 60 grams of fat.
- In a town there are 1,462 houses, of which 1,200 are connected to the gas network: 1,200 / 1,462 x 100 = 82.079 In other words, 82% of the houses are connected to the gas network.
- A water tank with a capacity of 80 liters has 28 liters. 28/80 x 100 = 35. This means that the tank is 35% full.
- In a botanical garden, out of 230 species, 140 are indigenous. 140/230 x 100 = 60.869. In other words, 60.8% of the species are autochthonous.
- Of a $ 100,000 prize, the winner must pay 20% in taxes. 20 x 100,000 / 100 = 20,000. In other words, the taxes are $ 20,000.
- A trouser that costs 300 pesos has a 25% discount. 25 x 300/100 = 75. In other words, the discount is 75 pesos and the final price is 225 pesos.
- 100 grams of rice contain 7 grams of protein. Since the total is 100, you don’t need to do the math: rice contains 7% protein.