1. The senior students in the school went boating. They calculated that if they added a boat. There are only six people on each ship; If one boat is reduced, it happens that each boat will take nine people. How many students are there in this class?

2. If A, B and C are three unequal natural numbers greater than 0, and a+b+c = 1 155, what is the maximum value of their greatest common divisor? What is the minimum value of the least common multiple? What is the maximum value of the least common multiple?

3. Two cars, A and B, are moving in opposite directions at the same time. They meet for the first time at a distance of 64 kilometers from B ... After the encounter, the two cars are still driving at the original speed. And after reaching the starting point of the other party, return immediately along the original road. On the way, the two cars met for the second time at 48 kilometers. How many meters apart are the two meeting points?

Three boxes contain fruits: one contains 50 apples, one contains 50 pears, and the other contains 25 apples and 25 pears. The three boxes are labeled with "50 apples", "50 pears" and "25 apples +25 pears" respectively. Now we know that the labels on these three boxes are all wrong (the labels don't match the real fruit inside). The question is, how many fruits can you at least take and judge what's in each of the three boxes?

5. On the first day, a pile of coal was transported, and on the second day, the remaining100t was transported, leaving 350 tons. How many tons is this batch of coal?

6. For the algebraic expression "5x", we can explain it as follows: someone walked for x hours at a speed of 5 km/h, and the distance he walked in a * * * was 5 km. Please give another explanation of "5x" in real life:

After working at an efficiency of 5/ min for x minutes, the total number of parts he made was 5x.

7. When the value range of x is x≥ 47, the value of formula -4x+| 4-7x |- 1-3x |+4 is constant, and this value is ().