In a school, senior students planted a batch of saplings. Senior students planted more than 25 trees in 5 / 8 of the total number, and the number of trees planted in the middle grade was 1 / 5 of that in the senior grade

In a school, senior students planted a batch of saplings. Senior students planted more than 25 trees in 5 / 8 of the total number, and the number of trees planted in the middle grade was 1 / 5 of that in the senior grade

How many seedlings are there in total
[25 + 25 * (1 / 5)] / [1-5 / 8 - (5 / 8) * (1 / 5)] = 120 (trees)

Four students went to plant trees. The first student planted half of the total trees planted by other students. The second student planted 13 of the total trees planted by other students. The third student planted 14 of the total trees planted by other students. Then the fourth student just planted 13 trees. How many trees did the four students plant?

The four students have planted 60 trees in total

In order to beautify the environment and carry out mass tree planting activities, a city planted 10 hectares of trees on tree planting day on March 12, 2007. If the annual tree planting area increases by the same percentage as that of the previous year, and 36.4 hectares of trees will be planted in the three years of 2009, what is the average annual tree planting Mu growth percentage compared with that of the previous year?

The result shows that the percentage of average annual tree planting per mu is x, then 10 + 10 (1 + x) + 10 (1 + x) 2 = 36.4. After sorting out, we get 25x2 + 75x-16 = 0, that is, (5x + 16) (5x-1) = 0, and the solution is X1 = - 3.2, X2 = 0.2

In the "tree planting day" activity on March 12, the school divided the tree planting tasks to the sixth and fifth grades according to the ratio of 5:3. In the sixth grade, 108 trees were actually planted, which exceeded 20% of the original assignment. How many trees were planned to be planted in the fifth grade?

（1+20%）x=108
x=90
90\5=18
18*3=54