2. Find eight even numbers less than 60 and make the sum of their reciprocal equal to 1.

In the following formula, all denominators are four digits. Please fill in a number in each box to make the equation hold:1□□□+11988 =1□□□□□

4. Among three digits, if the number on the tenth digit is greater than the number on the hundredth digit and the number on the single digit, it is called "convex number". So how many three-digit "convex numbers" are there in each number?

5. A batch of parts shall be equally distributed to Party A and Party B for simultaneous processing. B's work efficiency is 19/20 of A's ... When A completed half of his task, his work efficiency decreased by 5%, while when B completed half of his task, his work efficiency increased, so they both completed the task at the same time. What percentage has B's work efficiency improved? Please list the simplest arithmetic comprehensive solution! 〕

6. A store has two types of calculators *** 143, each 60 yuan for Type A calculator and RMB 37.8 for Type B calculator. A school bought all the B calculators and some A calculators in the shop. After accounting, it is found that the total amount payable has nothing to do with the total amount of type A calculators. What is the percentage of Type A calculators purchased? What is the total amount payable?

7. A group of passengers decided to take several big cars, each with the same number of people and duration. Each car took 22 people, and found that one person could not get on the car. If an empty car is driven away, all passengers just take the rest of the car equally. Each carriage can never carry more than 32 passengers. How many cars are there in the branch? How many passengers are there in this group?

8.a and B are 4800 meters apart. A lives in A, B and C live in B. One day they set out at the same time, B and C went to A, A went to B. After A and B met, B immediately turned back and marched, and 10 minutes later met C again. The next day, they set out at the same time, but the direction of A was opposite to that of the first day, but the speed of the three people did not change. After catching up with A, B immediately turned back to March and met C 20 minutes later. It is known that A walks 40 meters per minute to find the speed of C.

9. From 1 to 2004, how many * * * numbers carry at least 1 8866?

10. Without the number 3, how many 5-digit numbers can be divisible by 3?