1. Olympiad math test questions and answers in grade five of primary school.
There are only 15 seats in a row of chairs, and some seats have been taken. When Lele comes, no matter which seat he sits in, he will be adjacent to the person sitting. Q: How many people has Lele sat before? Seats numbered 15 are 1: 15. If seats 2 and 5 are already taken, the people sitting in seats 1, 3, 4 and 6 will be adjacent to those sitting in seats 2 or 5. According to this idea, No.2, No.5, No.8, 1 1 4 are all occupied, which means that these five seats are occupied in advance, so Lele will be adjacent to the seated person no matter which seat it sits in. So the answer is five people.
2. Question and answer of Olympic Mathematics in the fifth grade of primary school
1. There are 77 workers in a workshop. It is known that each worker can process 5 copies of Class A, 4 copies of Class B or 3 copies of Class C on average every day. However, processing three A-type parts, one B-type part and nine C-type parts is just one set. How many workers do you need to arrange for each of the three parts A, B and C, so that all the three parts A, B and C can be assembled? Solution: Suppose there are X kinds of parts after machining.
3/5X+ 1/4X+9/3X=77
x=20
A: 0.6×20= 12 (person) B: 0.25×20=5 (person) C: 3×20==60 (person).
My brother is three times as old as his brother. My brother is the same age as his brother. The elder brother and younger brother are 30 years old. How old are the younger brother and younger brother?
Solution: Suppose my brother is now X years old.
x-(30-x)=(30-x)-x/3
x= 18
Brother 30- 18= 12 (years old)
3. Question and answer of Olympic Mathematics in the fifth grade of primary school
For any two different natural numbers, replacing the larger number with the difference between these two numbers is called transformation. For example, 18 and 42 can be changed continuously:18,42→18,24→18,6→12,6→ 6,6. Until the two numbers are the same Q: What are the two identical numbers obtained from the two continuous transformations of 12345 and 5432 1? Why? If the common divisor of two numbers is a, then the common divisor of the difference between these two numbers and any one of these two numbers is also a, so in the process of each transformation, the common divisor of the two numbers is always the same, so the two same numbers finally obtained are their common divisors. Because the divisors of 12345 and 5432 1 are all 3, the two same numbers are all 3.
4. Question and answer of Olympic Mathematics in the fifth grade of primary school
1, calculation: 9.9×9.9+ 1.99 solution: of the two factors of 9.9×9.9 in the formula, one factor is enlarged by 10 times, and the other factor is reduced by 10 times, and the product remains unchanged, that is, the product can become 99× 1.99 can be divided into the sum of 0.99+ 1 After this change, the calculation is simpler.
9.9×9.9+ 1.99
=99×0.99+0.99+ 1
=(99+ 1)×0.99+ 1
= 100
2. Calculation: 2.437× 36.54+243.7× 0.6346
Solution: Although the factors of the two multiplications in the formula are different, the numbers of 2.437 in the previous multiplication and 243.7 in the next multiplication are the same, but the positions of decimal points are different. If the decimal points of two factors in one multiplication are moved in opposite directions by the same number, so that the two numbers become the same, simple calculation can be made by multiplication and division.
2.437×36.54+243.7×0.6346
=2.437×36.54+2.437×63.46
=2.437×(36.54+63.46)
=243.7
5. Question and answer of Olympic Mathematics in the fifth grade of primary school
1, solution: x band 1 yuan, (28-x) X band 1 angle +0. 1 (28-x) = 5.5.
0.9x=2.7
x=3
28-x=25
A: There are three Zhang Yiyuan bills and 25 dimes.
2. Solution: Let 1 element have X, 2 yuan (x-2) and 5 yuan (52-2x).
x+2(x-2)+5(52-2x)= 1 16
x+2x-4+260- 10x = 1 16
7x= 140
x=20
x-2= 18
52-2x= 12
A: There are 20 1 yuan, 8 18 in 2 yuan and 2 12 in 5 yuan.
3. Solution: There are X pieces in 5 yuan, 7 yuan and (400-2x) pieces in 3 yuan.
7x+5x+3(400-2x)= 1920
12x+ 1200-6x = 1920
6x=720
x= 120
400-2x= 160
A: 3 yuan has 160 and 7 yuan and 5 yuan have 120.
6. Question and answer of Olympic Mathematics in the fifth grade of primary school
The engineering team needs to finish it within the specified date. If Team A does it, it can be finished on schedule. If Team B does it, it will be finished three days later than the stipulated date. If Party A and Party B cooperate for two days first, and then Team B does it alone, it can be completed as scheduled. How many days is the specified date? Answer and analysis:
From "If Team B does it, it will be completed three days later than the specified date; If Party A and Party B cooperate for two days first, and then Team B does it alone, it can be completed as scheduled. " ：
B working for three days = a working for two days.
That is, the work efficiency ratio of Party A and Party B is 3: 2.
The working time ratio of Party A and Party B is 2: 3.
The time ratio difference is 1 serving.
The actual time difference is 3 days.
So 3÷(3-2)×2=6 days, which is the time of A, that is, the specified date.
Equation method:
[ 1/x+ 1/(x+2)]×2+ 1/(x+2)×(x-2)= 1
The solution is x=6.