1. When processing a batch of parts, Party A will do it alone for 20 days, and Party B will do it alone every day 1/30. Now, two people have cooperated to complete these parts. Party A rested for 2.5 days, while Party B rested for several days, so it took 15 days to complete it all. B how many days did you rest?

Suppose b has rested for x days.

1/20 *( 15-2 5)+ 1/30 *( 15-x)= 1

x=3 75

B rested for 3.75 days.

2. There are 50 fewer peach trees in the orchard than apple trees, and the 1/3 of apple trees is equal to 40% of peach trees. The ratio of pear trees to apple trees is 2:3. How many are there in the orchard

1/3 of apple trees = 40% of peach trees.

Apple tree: peach tree = 40%: 1/3 = 6: 5.

50/( 1-5/6)=300 (tree)-apple tree

300*5/6=250 (trees)-peach trees

300*2/3=200 (tree)-pear tree

3. The height of a cylindrical container with a bottom radius of 6 cm is equal to that of a conical container with a bottom radius of 9 cm. Now, the conical container is filled with water and poured into the cylinder, and the water depth is lower than that of the container 1.5 cm. How many centimeters is the cylindrical container?

Set the cylindrical container to be x cm deep.

9 * 9 * 3 14 * x * 1/3 = 6 * 6 * 3 14 *(x * 4/5- 1 5)

x=30

The cylindrical container is 30 cm deep.