1. At the beginning of winter vacation, red scarf volunteers take part in community labor. 50% students sweep the corridor, and two-fifths students carry garbage. Of these students, 7 did both, accounting for 14% of the total number of volunteers. How many volunteers are there? Except the students who sweep the corridor and transport garbage, the rest of the students clean the windows. How many people clean the windows?
2. Fun Games three-person relay race. According to the requirements, the first person runs a quarter of the whole race, the second person runs150m, and the third person runs a third of the whole race to finish the race. How many meters is the relay race?
3. The base angle of isosceles triangle is half of the top angle. What is the vertex angle of this triangle?
The sum of the circumference and diameter of a circle is 20.7 meters. What is the area of this circle? (assignment 3. 14).
A four-digit 3()7 () can be divisible by 9 and 4 at the same time. What is the maximum number of such four digits? What's the minimum?
6. To make the six-digit 15ABC divisible by 36, the quotient obtained is the smallest. What numbers do A, B, C and C represent respectively? What is the biggest business?
7. Choose three numbers from the four numbers 0, 3, 5 and 7, and arrange them into three numbers that can be divisible by 2, 3 and 5 at the same time. What are these three digits?
8. Among the four digits which are divisible by 1 1, please arrange them in descending order.
9. How many four-digit numbers * * * with a unit number of 6 and divisible by 3?
10, put a few natural numbers 1, 2, 3,. . . . . Multiplied together, if it is known that the last 13 bits of this result are all exactly 0, what should be the minimum value of the last natural number?
1 1. There are three kinds of books in the corner: story books, science books and literature books. The number of story books accounts for two-fifths of the total, the number of popular science books is three-quarters of that of literature books, and literature books are 20 less than story books. How many books are there in the book corner?
12. The total age of a family of four is 87 years old. Father is 2 years older than mother, and son is 5 years older than daughter. Six years ago, the total age of this family member was 65. How old is the daughter of this family now?
13. Several students from a school participated in the TV invitational tournament of "Entering the Kingdom of Mathematics", and the ratio of the number of boys to the number of girls was 8; 5. Later, 20 girls signed up for the competition. At this time, the number of girls accounts for 5/ 1 1. How many students are taking part now?
-Final collector: apple juice