Paper I · 9 Logical Reasoning & Analytical Ability · APPSC Paper I
9.3 Percentages and commercial arithmetic notes
13 notes, in reading order.
- 9.3.1Percentages: fraction equivalents and successive change
A percentage is a fraction with denominator 100; turn every change into a multiplier, and successive changes become a single multiplication.
Standard · 6 min · Full course - 9.3.2Profit and loss: cost price, selling price and profit per cent
Profit and loss per cent are always worked on the cost price unless the question says otherwise, and every sale is just a multiplier on the cost.
Standard · 5 min · Full course - 9.3.3Marked price, discounts and the dishonest dealer
Discount is taken on the marked price and profit on the cost price; keep the two bases apart and every markup–discount question becomes CP × markup × (1 − discount).
Standard · 5 min · Full course - 9.3.4Simple interest
Simple interest is charged only on the original principal, so it grows by the same amount every year and every question reduces to SI = PRT/100.
Standard · 5 min · Full course - 9.3.5Compound interest and the CI–SI difference
Under compound interest each year's interest is added to the principal, so the amount grows by a fixed multiplier, and the gap over simple interest is "interest on interest".
Standard · 5 min · Full course - 9.3.6Percentage applications: population, depreciation, elections and exam marks
Population and machine-value questions are compound interest in disguise, while election and exam questions are about finding the right base: valid votes, votes polled or maximum marks.
Standard · 6 min · Full course - 9.3.7Price, consumption and expenditure; income and savings
Expenditure = price × consumption and savings = income − expenditure; write each as a product or difference of multipliers and the question solves itself.
Standard · 5 min · Full course - 9.3.8Successive discounts, offers and comparing deals
Successive discounts multiply, free goods are a discount on the total handed over, and the cheapest deal is the one with the smallest final multiplier on the marked price.
Standard · 5 min · Full course - 9.3.9Instalments: equal payments under simple and compound interest
An instalment plan is fair when all payments, moved to one common date at the given rate, equal the debt moved to that same date: the due date for simple interest, today for compound interest.
Standard · 5 min · Full course - 9.3.10Compound interest: half-yearly and quarterly compounding, varying rates and growth
More frequent compounding means a smaller rate applied more often; convert every question into "rate per period, number of periods" and the formula A = P(1 + i)ᵐ does the rest.
Standard · 5 min · Full course - 9.3.11True discount and banker's discount
True discount is the simple interest on the present worth, banker's discount is the simple interest on the full amount, and the banker's gain is the gap between the two.
Standard · 4 min · Full course - 9.3.12Stocks and shares: face value, market value, dividend and yield
Dividend is paid on the face value but you pay the market value, so the real return is dividend ÷ market price, and "x% stock at y" means Rs y buys Rs x of yearly income.
Standard · 5 min · Full course - 9.3.13GST, commission and brokerage in everyday arithmetic
GST is a percentage added on the value after discount and collected stage by stage on the value added; commission and brokerage are percentages of the value an agent handles.
Standard · 6 min · Full course
Practise Percentages and commercial arithmetic. Questions with answers explained, from the same topics.
Medha AI is an independent preparation service. It is not affiliated with, endorsed by or connected to APPSC, TSPSC, MPSC, UPSC or any other commission or government body.