Estimate the total cost of two remote control cars, one costing ₹ 2172 and the other ₹ 1800, by rounding each cost to the nearest hundred before adding.

The cost is ₹ 2172. The tens digit is 7, so we round up.

$$₹ 2172 \approx ₹ 2200$$

The cost is ₹ 1800. This number is already a multiple of 100.

$$₹ 1800 \approx ₹ 1800$$

$$₹ 2200 + ₹ 1800 = ₹ 4000$$

The estimated total cost of both cars is ₹ 4000.

$$₹ 4000$$