ABSTRACT
At the end of this chapter, you should be able to:
• understand the term ‘percentage’ • convert decimals to percentages and vice versa • calculate the percentage of a quantity • express one quantity as a percentage of another quantity • calculate percentage error and percentage change
Percentages are used to give a common standard. The use of percentages is very common in many aspects of commercial life, as well as in engineering. Interest rates, sale reductions, pay rises, exams and VAT are all examples of situations in which percentages are used. For this chapter you will need to know about decimals and fractions and be able to use a calculator. We are familiar with the symbol for percentage, i.e. %. Here are some examples. • Interest rates indicate the cost at which we can
borrow money. If you borrow £8000 at a 6.5% interest rate for a year, it will cost you 6.5% of the amount borrowed to do so, which will need to be repaid along with the original money you borrowed. If you repay the loan in 1 year, how much interest will you have paid?
