The third grade math homework is surrounded by an 80-meter-long iron wire, which is 20 meters longer than the width. How to calculate the area?
The circumference is 80 meters, divided by 2 is the sum of length and width, which is 40 meters. Because the length is 20 meters more than the width, we can know that the length is 30 meters, the width is 10 meters, and the area is 30× 10=300 square meters. The specific solution can be set to a length and b width, and then a+b = 40, a-b.