Nandini hands over a ₹500 note for groceries costing ₹243.75. How much change (in ₹) should she get back?

Step 1: ignore the decimal points and multiply as whole numbers. Step 2: in the answer, place the decimal point so the **total decimal places equals the sum of the decimal places in the two factors**.

Example: $0.6\times 0.4$. Whole-number multiply: $6\times 4=24$. Total decimal places: 1 + 1 = 2. Place decimal: 0.24.

Example: $1.25\times \mathrm{0.3.125}\times 3=375$. Decimal places: 2 + 1 = 3. Place: 0.375.