Percentages in real world
Keywords: math, divide, percentage, interest, persent change Around the year 1260, the philosopher Roger Bacon wrote: “Mathematics is the door and the key to the sciences... for the things of this world cannot be made known without a knowledge of mathematics”. Centuries later this is as true as ever.
Mathematics is unique. It is both a beautiful and fascinating world of abstract structures and ideas and a down-to-earth, practical subject at the heart of modern science and technology. Much of its attraction comes from studying the relationship between theory and practice – an elegant theorem on complex functions, for example, also governs the lift on an aircraft wing, and apparently highly abstract algebraic results have important consequences in data security.
There is one of the way to express how large/small one quantity is, relative to another quantity in math we use percentage. A percentage is a part of something expressed as a value out of a hundred. Percentages are an important part of our everyday lives. Some examples include: sales and discounts
percentage chance of rainfall
statistics and survey results
Percentage is a very handy way of writing fractions.
Percentages can be compared more easily than fractions(fraction (from Latin: fractus, "broken") represents a part of a whole or, more generally, any number of equal parts, for example, one-half, eight-fifths, three-quarters). A percent can always be written as a decimal, and a decimal can be written as a percent, by moving the decimal point two places to the right.
The history of percentages goes back to the ancient Egyptians who wrote numbers (based on tens) alongside pictures called hieroglyphs. The idea of expressing parts of the whole are constantly in the same proportions, due to practical considerations, was born in ancient times from the Babylonians, who used the sexagesimal fractions. Already in Babylonian cuneiform tables are problems on the calculation of interest. Interest and have been known in India. Indian mathematicians calculated the percentages, using the so-called rule of three, that is, using a proportion.
1)To calculate a percentage value from absolute numbers
Peter scores 25 out of 32 in an exam, what is his result as a percentage?
To calculate Peter’s percentage score it is necessary to change '25 out of 32' into '? out of 100'. So:
This is done by multiplying the actual score by 100:
25/32 x 100 = 78%
So 25/32 is the same as 78/100
So John got 78% in his exam.
2)To calculate the true value a percentage represents
A camera normally costs Ј120 but in the sale it has been reduced by 15%. How much discount does this represent? (ie 15% of 120)
15% of 120 = 15 'out of 100' of 120.
15 'out of 100' can be written as 15/100
Therefore 15% represents Ј18 discount on the camera, the sale price being Ј102 (Ј120 less discount Ј18).
3)To calculate percentage increases and decreases
Percent increase and percent decrease are measures of percent change, which is the extent to which something gains or loses value. Percent changes are useful to help people understand changes in a value over time. Let's look at example of percent increase and decrease.
A particular brand of milk cost 35 per bag last week. This week it costs 42 per bag. By what percentage has the price risen?
Percentage increase = Actual increase/Original value x 100
In these example:
actual increase = 42 - 35
= 7/35 x 100
= 0.2 x 100
The price has risen by 20%.
4)To compare or combine results with different base values
Dina sat two exams last week. In science she scored 68 out of 100. In maths she scored 39...
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