Mathematics
Mathematics in the Bihar D.El.Ed paper covers number system, percentage, profit and loss, simple and compound interest, ratio, average, time-work, speed-distance, mensuration, and basic geometry. Most questions are one- or two-step calculations, so formula recall and clean arithmetic decide the score.
Core rules
- Percentage change = (change ÷ original value) × 100.
- Profit% and loss% are calculated on cost price unless stated otherwise.
- Simple interest = P × R × T ÷ 100.
- Average = sum of values ÷ number of values.
- Area of rectangle = length × breadth; area of circle = πr².
Worked example
An article costs ₹400 and is sold for ₹460. Find the profit percentage. Reasoning: profit = 460 − 400 = ₹60. Profit% = profit ÷ cost price × 100 = 60 ÷ 400 × 100 = 15%. Answer: 15%.
Traps
- Calculating profit% on the selling price instead of the cost price.
- Forgetting to convert units, such as metres to centimetres, before using a formula.
- Treating average as a total rather than a per-item value.
- In time-work, adding times directly instead of adding work rates.
Write the formula first, then substitute values; this reduces avoidable errors under exam pressure.