Xiao Ming has to go to school at 8:00 in the morning, but the alarm clock at home stops at 6:10. He wound up enough, but he forgot to check his watch and left. When he went to school, he was 10 minutes ahead of time. After school at 12:00, Xiao Ming came home and looked at the clock at 11:00. If Xiao Ming went to school and went home at the same time, how many minutes did his alarm clock stop?

Xiao Ming has to go to school at 8:00 in the morning, but the alarm clock at home stops at 6:10. He wound up enough, but he forgot to check his watch and left. When he went to school, he was 10 minutes ahead of time. After school at 12:00, Xiao Ming came home and looked at the clock at 11:00. If Xiao Ming went to school and went home at the same time, how many minutes did his alarm clock stop?

Xiaoming's time from leaving home to going home is: 11:00-6:10 = 4 (hours) 50 (minutes), Xiaoming's time to school is 10 minutes to 8 o'clock, 12:00-7:50 = 4 (hours) 10 (minutes), Xiaoming's time to school is: (4 hours, 50 minutes - 4 hours

Divide the bottom surface of a cylinder with a height of 3 decimeters into many equal sectors, and then cut the cylinder to form an approximate cuboid with the same height as its bottom. Its surface area is 36 square decimeters larger than the surface area of the cylinder. Calculate the volume of the cylinder

The radius of the bottom of the cylinder is: 36 △ 2 △ 3 = 6 (decimeter), the volume of the cylinder is: 3.14 × 62 × 3, = 3.14 × 36 × 3, = 339.12 (cubic decimeter); a: the volume of the cylinder is 339.12 cubic decimeter

28 trees are planted on one side of a 50m long road. However, at least () trees are planted, and the distance between them is not more than 2.5m
A.12                    B.9                         C.4  

B
50/2.5=20
28-20=8
8+1=9