Numerical Ability
What this domain tests
Numerical Ability covers arithmetic operations, fractions/decimals/percentages, ratio and proportion, averages, simple interest, basic geometry (perimeter, area, volume), unit conversion, and word problems. Speed and accuracy both matter, so estimation and shortcut methods are as important as formal computation.
Concepts to master
- Percent translation. "Of" means multiply, "is" means equals. Convert percent problems into equations: What is 15% of 240? → 0.15 × 240.
- Percent change. Change ÷ original × 100. A 20% increase followed by a 20% decrease does not return to the original value; use multipliers (1.20 × 0.80 = 0.96).
- Ratios. Combine ratios by matching the shared term; total parts = sum of ratio terms.
- Averages. Average = sum ÷ count. If a new value is added, update both sum and count-never average the two averages.
- Work and rate. Rate = work ÷ time; combined rates add. Distance = rate × time.
- Interest. Simple interest = principal × rate × time; keep rate as a decimal and time in years.
Traps that appear
Mixing units (minutes vs. hours, cm vs. m), forgetting to convert a percent to a decimal, and answering the wrong quantity (the discount rather than the final price). In geometry, radius vs. diameter and perimeter vs. area are frequent confusions. Some items ask for an approximation-do not over-calculate.
Rule of thumb
Estimate first to bound the answer, then compute exactly only if two choices remain close. For percent chains, multiply factors rather than adding percentages.
Worked example: A jacket costs ₱1,200 and is discounted 25%, then a further 10% off the sale price. Final price = 1,200 × 0.75 × 0.90 = 1,200 × 0.675 = ₱810. Note the total discount is 32.5%, not 35%.