Dao Elementary School Math Problems, 15 points! Urgent!

1.There are two sets of numbers, the average of the first group is 1280, the average of the second group is 1028, and the average of the two groups is 1208, so what is the ratio of the number of the first group to the number of the second group? 1280 to 1208 = 160 to 151 The ratio of the number of the first group to the number of the second group is 160 to 151 2

A and B set off from AB at the same time, walking in the opposite direction, met on the way, after the two continued to walk, A arrived at B and returned immediately, and caught up with B at more than 200 meters above the meeting point, it is known that the speed ratio of A and B is 9:2, how many meters apart is AB? (9-2) 200 = 1400 (m) ab 1400 m apart.

3.There are two kinds of work, A and B, Xiao Zhang does it alone, it takes 10 days to complete work A, and 15 days to complete work B; Xiao Li does it alone, it takes 8 days to complete work A, and 20 days to complete work B. How many days does it take for two people to complete these two tasks together?

1 (1/10 + 1/8) = 40/9 (days) It takes at least 40/9 of a day for two people to complete these two tasks together!

1. (1280x+1028y) (x+y)=1208 to obtain the ratio of the number of the first group to the number of the second group: x y=5:22, let the speed of A be 9V, and the speed of B be 2V; The AB distance is S, the first meeting time of A and B is t1, and the second meeting time is t

9vt1+2vt1=s

9vt=9vt1+2*2vt1+200

9vt=2vt+s

Solve the above equation for s = 1925 meters.

15-8) (7 4) = 12 (days).

A, B, C and D stand in a row, take a total of 35 flowers, A right 16, C right 4, D right 25 to see the question, C right 4, C right someone, A and D If C is on the right side, the number is not right, exclude, therefore, there is only B on the right side of C, B takes 4 flowers.

A and D are on the left side of C, there are two situations, one is A on the left side of D, the other is on the right side of D, if A is on the left side of D, 16 on the right side of A, and 25 on the right side of D, the number of D on the right is wrong, so it can only be D on the far left.

The order is. D, A, C, B.

After the calculation. D, A, C, B.

A 9 flowers, 4 flowers, C 12 flowers, Ding 10 flowers.

1.Use the easy method to calculate the following questions (off-style).

2.The least common multiple of two prime numbers is 51, and the two prime numbers are (3) and (17).

3.Judgment. There are no prime factors other than the denominator, and such a fraction cannot be reduced to a finite decimal (

There is no common divisor () for the denominator and numerator of the simplest fraction (

The fractions are all smaller than the integers (

4.The edge length of a cube is 2 times larger, its surface area is (4) times larger, and its volume is (8) times larger.

5.Flatten two equal cubes into a cuboid, the surface area of the cube is reduced by 32 square centimeters. The surface area of the assembled cuboid is (160) square centimeters, and the volume is (128) cubic centimeters.

6.A cube tank with a solvent of 105 cubic decimeters, fill it with water and pour it into a rectangular tank 6 decimeters long and 5 decimeters wide, which is exactly full. How many decimeters is this cuboid tank? (Column Equation and Result).

7.Seven-fifteenth meters means that 1 meter is divided into (15) parts, and (7) parts of them are taken to obtain the number: It can also be said to divide (7) meters into (15) portions equally, and take the number of one of them.

8.A fraction, the numerator remains the same, and the denominator is expanded by a factor of 4, and the fractional value is (b).

a。No change b. Quadruple c. Quadruple shrink.

9.A number divided by twelve, Xiao Ming sees 12 as 18, and the resulting quotient is 20, what is the correct quotient? (Columnar Write Result).

10.Three consecutive odd numbers, the middle one is a, and the other two are (a-2) and (a+2) respectively

， ，43/52，6/7，,2/440

True True False.

Fifteen Seven Seven Seventy Fifteen.

c18*20/12=30

a-2 a+2