1。 The least common multiple of 18 and 60 is 180, so the interval between the first and second lighting and ringing is 180 minutes, so the next lighting and ringing is at 4 o'clock.

2。 When the number of books on the first floor is set to A after taking 33 books, there are 2a+6 books on the second floor, 2a+6+a+33= 168, a=43, and there are 92 books on the second floor.

3。 A circle is 180m, and twice the width plus 40m equals 90, so the width is 25m and the length is 65m.

4.2 divided by 3, 2 divided by 7, so 2 divided by 2 1, the least common multiple of 3 and 7, 2 divided by 2 1, we will think of 23 first; 23 is divisible by 5, so 23 is the smallest number.

5。 A multiple of 2 and 5, so the last number is 0, which is a multiple of 3. The penultimate number can be one of 369, because it is the largest number, so the penultimate number and the third number are both 9,33875990.