Solution: 3m = 2 1, m = 7.
Least common multiple: 2× 3× 2 1 = 126.
2. Fold a rope into 5 strands and 6 strands respectively. If 5 strands are 20 cm longer than 6 strands, then the length of this rope is () meters (note that it is meters).
Solution: x/5-x/6=20
x=600
The length is 6 meters.
3. The average of the numbers A, B and C is 70, A: B = 2: 3, B: C = 4: 5, and the number B is ().
Solution: Let A be 8x, B be 12x and C be 15x.
(8x+ 12x+ 15x)/3=70
x=6
B is 72.
4. The decimal point of the number moves one place to the right and then three places to the left. The new number is 34.65 less than the original number, which is ().
Solution: 0.99x=34.65
x=35
The original number was 35.
5. When the area formula of the circle is pushed down, the circle is divided into several equal parts and put together to form an approximate rectangle. It is known that the length of a rectangle is 6.42 centimeters more than the width, and the area of a circle is () square centimeters?
Solution: 3. 14r-r=6.42.
r=3
S=3. 14×9=28.26 cm2。
Give five identical gifts to three children, so that each child can get a gift. There are () different ways to give gifts.
Solution: 6
1、 1、3
1、3、 1
3、 1、 1
1、2、2
2、 1、2
2、2、 1
7. For the sake of students' hygiene, the school provided each boarder with a water cup and a 3 yuan. 10% discount for Ocean Mall, and "buy eight and get one free" for Baihui Commercial Building. Where is the right place to buy 180 cups at school?
Solution: Ocean: 3× 180× 0.9 = 486.
Baihui: 180× 8/9× 3 = 480
Baihui is suitable.
8. In the two-story summer vacation, there are more books upstairs than downstairs 18. If you take out the book 10 1 from the upper floor and put it on the lower floor, then the books on the two floors are equal. How many books are there on the upper and lower floors? (Equation solving)
Solution: let the lower level have x copies.
3x+ 18- 10 1 = x+ 10 1
2x=202- 18
x= 10 1-9=92
Upper layer: 92× 3+ 18 = 294.
9. Students from a school have a spring outing. If you rent a 45-seat bus, 15 people have no seats. If you rent the same number of 60 buses, one bus is empty. It is known that 220 yuan rents 45 buses and 300 yuan rents 60 buses. (1) How many students are there in this school? (2) How to rent a car is the most cost-effective?
Solution: There are X students.
(x- 15)/45=x/60+ 1
4x-60=3x+ 180
x=240
300÷60=5
220 \45 = 44/5 & lt； five
So use a 45-seat car.
220× 4+300 = 1 180 yuan.
Four cars with 45 seats and one car with 60 seats.