Solution:
Price of 1 kg plastic = ₹ 10
The total price for 22 kg plastic = 22 × ₹10 = ₹220
Price of 1 kg iron = ₹ 12
The total price for 12 kg iron = 12 × ₹12
This can be rounded off as 12 × ₹10 = ₹120
Thus, the estimated cost will be = 220 + 120 = ₹ 340
Hence, the approximate cost will be ₹340.