Find the simple interest on ₹1000 for 2 years at 5% per annum.

₹100

Simple Interest = (P × R × T)/100 = (1000 × 5 × 2)/100 = ₹100. The principal amount stays the same each year.

Understanding Arithmetic questions

Arithmetic questions test fluency with percentages, ratios, averages, profit and loss, and time-related problems. Speed here frees up time for harder sections in any timed paper.

How to approach it

1. Convert every quantity to the same form — fraction, decimal or percentage.
2. Write the relationship as a single equation before calculating.
3. Use unitary method for ratio and proportion problems.
4. Estimate the answer first so an arithmetic slip is obvious.

Common mistakes to avoid

• Taking a percentage of the wrong base value.
• Averaging averages instead of using total ÷ count.
• Mixing up cost price and selling price in profit questions.

Where it appears: Core to CBSE Class 5–10 and the backbone of most aptitude and entrance papers.