1. According to statistics, China wastes about 10% of the country's total output every year. If everyone can CD-ROM, it can save 50 billion Jin of grain every year. In the title, China's total grain output is regarded as 1, and China's total annual grain output is about (500 billion) kilograms. If everyone needs to eat 250 kilograms of food every year, the food saved by CD-ROM can feed (2 billion people) for one year.

2. Repairing a section of road, four fifths of the total length was repaired on the first day, four fifths of meters were repaired on the second day, and there were more on the first day.

3. According to the fact that the output is increased by one fifth than planned, the following description is wrong (c).

In question A, the planned output is taken as the unit 1 B, which is actually equivalent to the planned output (1+ 1/5).

C planned output is equivalent to actual (1+ 1/5) d actual output /( 1+ 1/5) = planned output.