Please use proportion to solve the math problems in the sixth grade of primary school, and write out the ideas and steps to solve the problems. Other problem-solving methods and no problem-solving ideas are invalid. Satisfied answer! 1: Idea: Let the apple be X, because the apple is 320kg lighter than the orange, so the orange is x+320.

5/7=x/(x+320)

5x(x+320)=7x

5x+ 1600=7x

1600=2x

x=800

2 train of thought: first calculate the area of the classroom and the area of the square brick, and then divide the area of the classroom by the area of the square brick to get the number of blocks used.

Solution: 0.4/275=0.5/x

275x0.5=0.4x

x= 176