# Mathematic – Percentage Calculation

by Lau Hao Ying
(Singapore)

In a school of 1800 pupils, 324 pupils wear glasses. What percentage of the pupils
do not wear glasses?

### Comments for Mathematic – Percentage Calculation

 Oct 08, 2012 Percentage Calculation by: Staff Answer:Part ICalculate the number of pupils who do not wear glasses(Pupils who wear glasses) + (Pupils who DO NOT wear glasses) = (Total number of pupils)324 + (Pupils who DO NOT wear glasses) = 1800(Pupils who DO NOT wear glasses) = 1800 - 324(Pupils who DO NOT wear glasses) = 1476Pupil and Glasses SummaryPupils who wear glasses = 324Pupils who DO NOT wear glasses = 1476Total number of students = 1800What percentage of the pupils do not wear glasses?` number without glasses% NO GLASSES = -------------------------- * 100 total number of students 1476% NO GLASSES = ------- * 100 1800% NO GLASSES = 82 % ` The final answer is: 82%-------------------------------------------------------------------------------The question you may be asking yourself about now is probably something like this:Why not just use the numerical total for the number of pupils who DO NOT wear glasses? 1476 pupils is straightforward and easy to understand.This is why:Percents are a CONVENIENT WAY to EXPRESS a PROPORTION. Calculating a percent may be extra work. However, once the percent calculation has been completed, PERCENTS are EASY TO UNDERSTAND and EASY TO USE. PERCENTS are EASY TO UNDERSTANDFor example, suppose two students have the following academic averages: 84% and 86%. It is easy to see that (all other things being equal) the student with the 86% average is the better student. All anyone has to do is look at the numbers. 86% is a bigger number than 84%. 86% is better than 84%. Even if the person reading the two numbers (84% & 86%) has no idea how a percent is calculated, they still understand that 86% is bigger and better than 84%. What percents actually mean: I will continue to use the example of the two students who earned the 84% and 86% averages. For this example, the students earned their percentage scores entirely from multiple choice tests. (Students in the real world do more than just take multiple choice tests. However, for this example that’s all they do.) 84% means that for every 100 multiple choice questions this student attempted to answer, this student answered 84 correctly. -----------------------------------------------