Olympiad math problems in grades five and six.

The math quiz group will answer your questions, hoping to help you.

An engineering team has to do two projects, A and B. The workload of A is twice that of B. In the first half of the month, the whole team is doing A, while in the second half, half is doing A and half is doing B. After a month, A project is completed, and the remaining workload of B project needs 1 person for one month. How many people are there in the engineering team?

{[2/(1+2)]/[1-2/(1+2)]/(1/2) = 8 people.

It is known that C is the midpoint between A and B. A leaves from A to B at 8 am, while B and C leave from B and C respectively. When A meets C, B just walks to C. When 10a. m. B walks to A, A is 20 kilometers away from B, and C arrives at A at11A.M., then A and B are two places.

On 10 in the morning, Party B walks to Station A, which means that the whole journey takes Party B 10-8=2 hours;

In the morning 1 1 point, c arrives at location a, which means the whole journey takes 2*( 1 1-8)=6 hours.

When A and C meet, B just goes to C, which means that it takes 2/2= 1 hour for A and C to meet; At this time, Party C walked the whole journey 1/6, while Party A walked the whole journey1/2-1/6 =1/3, which took 3 hours.

10 in the morning, when b walks to a, the distance between a and b is 20km, which means that the speed of a is 20/[3-(10-8)] = 20km/h;

Therefore, the distance between A and B is (20*3=60) kilometers.

24*43 5 1+5 1*43 19

=5 1*43 24+5 1*43 19

= 51* (24 of 43+65438 of 43+09)

=5 1* 1

=5 1

In physical education class, Mr. Wang asked the students to count to 1-2, then to 1-3, and finally to 1-7. He asked Xiao Ming, who was ranked last, "How many times did you report it three times?" Xiaoming said, "I always quote 2." Teacher Wang said, "I see that there are 1 people absent from class today in your class." There are () students in this class.

2*3*7+2+ 1 = 45

Party A and Party B go hand in hand. When meeting for the first time, Party A is 40 meters away from the starting point, and when meeting for the second time, Party B is 20 meters away from the starting point. How many meters are they apart?

40+[40+(40 * 2-20 * 2)/2)] =100m

The distance between Party A and Party B is100m.

There are 48 fifth-grade students in the art group, three times more than those in the science and technology group. How many people are there in the science and technology group?

( 48-6)/3= 14

It takes 8 hours for the train to go from A to B, 6 hours for the bus to go from B to A, 2 hours for the train to leave A, and 30 kilometers for the bus to go from B to A. What's the distance between a and b?

It takes 8 hours for the truck to get from place A to place B, that is, it takes 4 hours for the truck to reach the midpoint.

At this time, the bus takes 4-2=2 hours, and the bus takes 6 hours from B to A, so the bus has not yet reached the midpoint;

Therefore: 30/{1/2-1/6 * [(1-1/8 * 2)/(1/8+1/6)] = 40.

The distance between Party A and Party B is 420 kilometers.

It takes 8 hours for a ship to sail downstream from Port A to Port B, and when it returns, it travels 9 kilometers less than downstream. It is known that the distance between Port A and Port B is 2 16 km. Then: 1. How many hours did I come back than when I went? 2. How many kilometers is the speed of water flow per hour?

1, 4 hours more when I came back than when I went.

9*8 /(2 16/8 -9)=4

The speed of water flow is 4.5 kilometers per hour.

9/2=4.5

60, 45 and 80 are divisible by a number. What is the maximum quantity?

60=2*2*3*5

45=3*3*5

80=2*2*2*2*5

Visible greatest common divisor 5,

So, if you divide 60, 45 and 80 by a number, they are divisible, and the maximum number is 5.

Two people, Party A and Party B, process parts and make 224 pieces in 8 hours. Party A makes 2 more pieces per hour than Party B. How many pieces does Party B make per hour?

(224-2*8)/(2*8) = 13

B production per hour 13 pieces.

A pile of pears, three with three more than one, four with four more than three, five with five less than one, there are at least a few pears in this pile.

Four sizes four are more than three, and five sizes five are missing one. Note: plus 1 is a multiple of 4 and a multiple of 5, so the unit number is 9;

The remainder of three numbers indicates that negative 1 is a multiple of 3, and 9- 1=8. When the decimal number is 1, 18 is a multiple of 3 and the smallest. So there are at least 19 pears in this pile.

In the division formula, the product of dividend (nonzero), divisor and quotient is divided by dividend, and dividend is ().

A section of road has been repaired by four fifths, that is, 40 kilometers. How many have not been repaired?

40/(4/5)-40 =10km

There is still 10 km not repaired.

The average price of three kinds of cloth is 0.45 yuan per foot. A is 8 points more expensive than C, and B is 4 points more expensive than C. How much are all kinds of fabrics?

C (0.45 * 3-0.08-0.04)/3 = 0.41yuan.

A 0.4 1+0.08=0.49 yuan.

Type b 0.4 1+0.04=0.45 yuan.

① The product of two numbers A and B is 4/7 of A and 3/5 of B, so what is the product of two numbers A and B? ② Drink a 20% glass of milk, add water and mix well, and then drink 50% pure milk, which accounts for a few percent of the volume in the glass?

(3) The passenger car and the truck run in opposite directions from the middle point between A and B. At 5 o'clock, the passenger car arrives at A, and the truck is 60km away from B. It is known that the truck and the bus are 5:7, so how far is A and B?

(4) Party A and Party B cooperate for 36 days, and Party B and Party C cooperate for 45 days ... Now, after Party A, Party B and Party C cooperate for 15 days, Party B will complete the remaining projects for another 30 days. How many days does it take to finish the work alone?

①4/7 * 3/5 = 12/35

② 1-20%=80%

③60/(7-5) *(7+7) = 420km

④1{[1-(1/36+1/45) *15]/(15+30-15 *)

At the same time, Party A and Party B set out from their respective homes, which are1340m away, and walked towards each other. Party A rides a bicycle for 250 meters per minute, and Party B walks for 90 meters per minute. After 3 minutes, Party B returned home and picked up the forgotten books. A few minutes later, Party A caught up with Party B? B how many meters away from home at this time?

[1340-(250+90) * 3]/(250-90) = 2 minutes.

90 * {3-[1340-(250+90) * 3]/(250-90)} = 90 meters.

Two minutes later, A caught up with B, and B was 90 meters away from home.

Xiao Fang's telephone number is seven digits, which is a multiple of 2, 3 and 5. It is known that the first three digits are 326, and the last four digits and 326 constitute the minimum number that meets the requirements. Can you guess the telephone number of Xiao Fang's home?

Is a multiple of 2, 3 and 5, and the mantissa is 0;

3+2+6= 1 1, plus 1 is a multiple of 3.

So the last four digits and 326 constitute the minimum number that meets the requirements, saying 32600 10.

The distance between the two places is 280 kilometers, and there are ships sailing inside. It takes 14 hour downstream and 20 hours upstream. Find the speed and current of the ship in still water.

One-dimensional linear equation method;

Solution: Let the ship's speed in still water be x km/h, then the current speed is 280/ 14 -x km/h, then there are:

20[x-(280/ 14 -x)]=280

Solution: x =17,280/14-x = 3.

Binary linear equation method;

Solution: Let the ship's speed in still water be x km/h, then the current speed is y km/h, as follows:

20(x-y)=280

14(x+y)=280

x= 17，y=3

A: The speed of this ship in still water is17km/h, and the current speed is 3km/h,

Algebraic method:

Velocity in still water: (280/14+280/20)/2 =17 km/h,