1 out of every 5 people is in the fourth grade, which means that the winning percentage of the fourth grade is 1/5 = 20%.

There are 1 in every four people in the fifth grade, which means that the winning percentage of the fifth grade is 1/4 = 25%.

You should be able to figure out this step.

The first question: because the winning rate is 100% (this is nonsense again. . . )

However, the percentage of winners in Grade 4 and Grade 5 is always the same, so the percentage of winners in Grade 6 is 100%-20%-25% = 55%.

The second question: Twenty-five people won the prize in the fifth grade, because the percentage of winning the prize in the fifth grade is 20%. Based on this, we can get the total number of winners: 25/25%= 100 (person).

After knowing the total number of winners, multiply the total number by the winning percentage of the sixth grade.

100×55%=55 (person)

(*^__^*)