General Mathematics and Arithmetic: Speed and Accuracy
Core Concepts
Topics include percentages, ratio and proportion, average, profit and loss, simple and compound interest, time-speed-distance, work, and basic algebra and geometry. Number series and simplification are common in written tests.
Traps to Watch
Percentage questions often ask for successive changes; two successive increases of 10% give 21%, not 20%. In profit and loss, always fix the cost price as the base unless stated otherwise. For compound interest, distinguish annual from half-yearly compounding. In time and work, remember that rates add, not times. In average problems, adding a new value changes both total and count. Watch units: convert minutes to hours before applying speed formulas.
Worked Example
A shopkeeper marks an item 25% above cost and offers a 20% discount. Selling price = 1.25 × 0.80 = 1.00 of cost, so profit is zero. Rule of thumb: multiply successive percentage factors; do not add them.
Study Strategy
Practice 20 mixed arithmetic problems daily under timed conditions. Memorize fraction-percentage equivalents (1/8 = 12.5%). Show units in every step to avoid conversion errors.