If the goods are discounted, the original price can be rounded off, estimated to be an easy-to-calculate integer, and then multiplied by the discount rate, which becomes simple.

For example, a dress costs 298 yuan, with a 20% discount, so 298 can be counted as 300, and the discounted price is probably 240 yuan. If it's a 6.9% discount, the quick oral calculation method is that 300 times 70% equals 2 10 yuan.