今天,我们学习了新知识——估算。没想到它却帮了我的大忙。放学以后,我陪妈妈一起去买西瓜。西瓜2.8元/千克,我们买了一个重6.9千克的大西瓜。卖西瓜的老板对我们说要付22.2元。我大脑一转,发现这个数不对。于是,我对老板说:“叔叔,应该不到20元吧!”老板又用计算器算了一遍,说:“对不起,应该付19.32元。” Today, we learn new knowledge - estimation. Did not think it helped me a lot. After school, I went with my mother to buy watermelon. Watermelon 2.8 yuan / kg, we bought a weight of 6.9 kg of watermelon. The owner selling watermelon told us to pay 22.2 yuan. I brain a turn and found that the number is wrong. So, I said to the boss: “uncle, it should be less than 20 yuan!” The boss again calculated with the calculator, said: “Sorry, you should pay 19.32 yuan. ”