Maths Unit 4

Reciprocals

The reciprocal of the number is n is 1/n, it can also be written as n to the power of -1
In order to find the reciprocal of a fraction, swap the numerator and the denominator. - Eg. 3/4 becomes 4/3
To find the reciprocal of a mixed number, you have to convert the number into an improper fraction

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You can compare ratios by writing them as unit ratios. In a unit ratio, one of the numbers is 1. The other number may or may not be a whole number
To share a quantity in a given ratio, you could work out what fraction of the total amount each person receives, then multiply each fraction by the total amount. Another method is to work out how much one part is worth, and then multiply by the number of parts each person receives
When two quantities are in direct proportion, as one is multiplied so is the other and as one is divided so is the other

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Simple interest is the interest calculated only on the original amount invested. It is the same amount each year
You can calculate a percentage change using this formula - percentage change = actual change/original amount x 100 - percentage loss (or profit) = actual loss (or profit)/ original amount x 100
You can use inverse proportions to find the original amount after a percentage increase or decrease

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Depreciates means losing value
Your income is the amount of money that you earn or are paid per year
When you are working out profits, remember to subtract any costs first
All recurring decimals can be written as exact fractions - If 1 decimal place recur, then multiply by 10 - If 2 decimal places recur, then multiply by 100 - If 3 decimal places recur, then multiply by 1000

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