Introduction
Percentage means "per hundred" (Latin per centum). A percentage is simply a fraction whose denominator is fixed at 100. When we say 25%, we mean 25 out of every 100, i.e. the fraction 25/100 = 1/4 = 0.25.
Percentage is one of the single most important chapters for every Bangladeshi government job exam — BCS, Bank (Senior Officer / Officer), Combined bank exams, PSC, and IT-officer written and MCQ tests. It is the backbone of profit-loss, simple and compound interest, discount, population growth, data interpretation, and many word problems. Mastering percentage lets you solve a large family of arithmetic questions quickly and accurately. Because these questions are usually calculation-heavy and time-limited, learning the shortcuts and the standard fraction equivalents is as important as understanding the concept.
Learning objectives
After finishing this lesson you will be able to:
- Define percentage and convert freely between percentages, fractions and decimals.
- Find a percentage of a quantity, and express one quantity as a percentage of another.
- Compute percentage increase and percentage decrease correctly.
- Handle successive (repeated) percentage changes without error.
- Find the original (base) value when a percentage change and the result are known — the classic "reverse percentage" trap.
- Apply percentage to real exam scenarios: profit and loss, discount, population, exam marks, and salary.
- Recognise and avoid the common conceptual mistakes examiners deliberately test.