When calculating water, gas and electricity charges, etc. There must be a ladder charge. For example, Zhang San, it was 300 degrees at the end of last month and 600 degrees this month. According to the regulations, the monthly electricity consumption is within 200 degrees (inclusive), and the unit price per degree is 0 50 yuan. If it exceeds 200 degrees, it is 0. 10 yuan per degree, which means 600-300=300. Zhang San uses 300 degrees this month. 200? 0.5+ 100x0.6= 160 yuan. Zhang San has to pay 160 yuan electricity bill this month. But students should master it all, not only know the methods, but also practice more. It is impossible to know everything only by theoretical knowledge in class.