Primary 4 Mathematics Olympiad

1.A barrel of oil was poured three times, each time with more than 1 kilogram of the remaining half, and finally 7 kilograms left. How many kilograms of oil was in this barrel?

7+1) 2=16 This is the second pour of the remaining oil.

16+1) 2=34 This is the first pour of the remaining oil.

34+1) 2=70 This is the original oil.

2.When Xiao Lin was doing the division test, she wrote the divisor 76 as 67, and the result was that the quotient was 17, and there was 1 remaining. What should be the correct quotient?

Use the wrong number and the wrong divisor to calculate the correct dividend.

Then calculate the correct quotient.

3.A number divided by 9 gives the same quotient and remainder, how many such numbers are there?

8 in total. 4.There are 50 students in the first class of the fourth grade, and in a math test, 30 people answered the first question correctly, 33 people answered the second question correctly, 22 people answered the two questions correctly, and how many people did not answer both questions correctly?

Since there are 22 people who have to answer the two questions correctly, there are only those who answer the first question correctly.

30-22 = 8 (people).

Again, so only the second question is answered correctly.

33-22=11 (person).

Well, there are those who didn't answer both questions correctly.

50-22-8-11 = 9 (people).

4.Answer: 30-22 = 8 = number of people who answered only 1 question correctly.

33-22 = 11 people who only answered 2 questions correctly.

8 + 22 + 11 = 41 The number of people who answer the question correctly (regardless of one question or two questions) Personal algorithm, no plagiarism!

The fourth grade of elementary school is in the same difference series! It's incredible, I only learned it in my first year of high school!!

1) Because an=a1+(n-1)d

So 78 = 30 + 24d d = 2

2）sn=na1+d*n(n-1)/2

So sn=25*30+25*24=1350

（78-30）/（30-25+1）

The 8 rear row has 8 more seats than the previous row.

1350 pcs.

There are 1,350 seats in total.

（1）78-30=48

24 more rows, 48 more in total, so 48 more per row 24 = 2 so the back row has 2 more seats than the previous row.

2) The average number of seats per row is (30+78) 2=5454 25=1350

The total is 1350.

(1) Because row 25 is the last row, the back row is more than the previous row (78-30) 24 = 2 seats.

2) The total number of seats can be added by inversion and then divided by 2 = (30 + 78) * 25 2

1350 seats.

The back row is more than the previous one:

78 30) (25 1) = 2 (pcs).

The number of seats for all is:

30 78) 25 2 = 1350 (pcs).

(1) The number of seats in each row is arranged in an equal difference series.

So the back row is more (78-30) than the previous row (25-1) = 2.

2) The number of seats is (30+78) 2*25=1350.

(1) The formula of the equal difference series an=a1+(n-1)d, d is the tolerance, that is, the number of seats in the back row is more than the previous row, and the value is brought into the above formula. a25 = a1 + (25-1) d, that is, 78 = 30 + 24 d, d = 2

2) The formula for summing the difference series is sn=n(a1+an) 2, and the substitution gives sn=1350

If the water can be drained in x hours, 1 pumping machine can pump the water in y hours by 20 x+5*20 y=1

15/x+8*15/y=1

x=75 y=2500/11

The efficiency of each pump is 1

The difference in the middle is due to the fact that the efficiency of the outlet can be found by leaking water through the outlet every hour: (120-100) (20-15) = 4 original water volume: 100 + 20 4 = 180

It takes 180 4 = 45 hours to drain water from the outlet alone.

The flow of water at the outlet is =(15*8-20*5) (20-15)=4

The water volume of all pools is =20*5+4*20=180

Therefore, the water is discharged only by the outlet, and the time is =180 4=45 hours.

5 pumps can be used to pump the water in 20 hours, which is equivalent to 1 pump in 100 hours and the water outlet in 20 hours;

It takes 15 hours to pump water from 8 pumps, which is equivalent to 120 hours with 1 pump and 15 hours at the outlet.

Then, the water output of the outlet in 1 hour is equivalent to the amount of water pumped by 4 pumps in 1 hour or the amount of water pumped by 1 pump for 4 hours.

Therefore, 1 pump pumps for 120 hours, which is equivalent to 30 hours of water at the outlet, plus 15 hours, so that the water leaks out of the outlet in 45 hours.

24 is not for 5th grade, note: other grades + 6th grade = 24 22 is not for 6th grade, note: other grades + 5th grade = 22 that is:

5th grade + 6th grade + two other grades = 24 + 22 = 46 panels.

There are a total of 10 calligraphy works exhibited in the 5th and 6th grades.

Description: 10 pictures + two other grade levels = 46 pictures.

46-10) 2=18 panels.

The landlord did the right thing, you can also tell me what you think.

There are a total of x frames for grades 1 to 4, y frames for grade 5, and z frames for grade 6.

Yes: x+z=24

x+y=22

y+z=10

The addition of one and two formulas yields: 2x+y+z=46 gives x=18, and the same obtains: y=4 z=6

So 18 pieces in total.

Solution: (24+22-10) 2=18 panels.

6th grade + other = 24

5th grade + other = 22 then 6th grade + 5th grade + other x2 = 24 + 22 = 46, other = (46-10) 2 = 18 pieces.

There were 24 non-fifth-grade and 22 non-sixth-grade;

i.e. there are 24 paintings in grade level.

There are 22 paintings in the grade.

Then the works of other grades are (22+24-10) 2=18 (frames) You did it right!!

It is known by the 6th grade that there are two more paintings than the 5th grade. 6 in 6th grade and 4 in 5th grade. 18 for other grades.