Problems and answers of Olympic mathematics in the fifth grade of primary school [5 articles]

# Elementary Olympiad # Introduction Olympiad has a certain effect on teenagers' mental exercise, which can exercise their thinking and logic, and plays a more profound role for students than ordinary mathematics. The following is the relevant information of "Five Questions and Five Answers of the Fifth Grade Olympiad in Primary School", hoping to help you.

1. Olympiad math test questions and answers in grade five of primary school.

A big car and a small car both drive from A to B. The speed of the big car is 80% of that of the small car. It is known that the bus leaves earlier than the car 17 minutes, but it stops at the midpoint of the two places for 5 minutes before continuing to the second place; However, after the bus set off, it didn't stop halfway, and went straight to B. Finally, the bus arrived at B 4 minutes earlier than the bus. It is also known that the bus departs from a place at 10 in the morning. So when did the bus catch up with the bus in the morning? Answer and analysis:

This topic is similar to question 8. But it's more complicated than question 8!

The bus is more than the car 17-5+4= 16 minutes.

Therefore, it takes 16÷( 1-80%)=80 minutes to complete the bus journey.

It takes 80×80%=64 minutes for the car to complete the whole journey.

Since the car has stopped at the midpoint, we have to discuss whether we can catch up at the midpoint.

The bus will reach the midpoint at 80÷2=40 minutes after departure, and leave at 40+5=45 minutes after departure.

The bus starts after 17 minutes, and the bus keeps running 17+64÷2=49 minutes.

It means that when the car reaches the midpoint, the cart has already started again. And then get caught in the second half of the road.

As neither of them had a rest, the bus arrived four minutes earlier than the bus.

Then the catch-up time is 4÷( 1-80%)×80%= 16 minutes ago.

So, after the bus leaves, 17+64- 16=65 minutes.

So the time at this time is 1 1: 05.

2. Question and answer of Olympic Mathematics in the fifth grade of primary school

1, A car and B car leave from AB at the same time. A walked 5/ 1 1 of the whole journey. If A drives at a speed of 4.5 kilometers per hour, B drives for 5 hours. How many kilometers are AB apart? Solution: AB distance = (4.5× 5)/(5/11) = 49.5 km.

2. A bus and a truck leave from Party A and Party B at the same time. The speed of a truck is four-fifths that of a bus. After a quarter of the journey, the truck and the bus met for 28 kilometers. How many kilometers is it between A and B?

Solution: When the speed ratio of bus and truck is 5: 4, the distance ratio when they meet is 5: 4, which is 4/9 of the whole journey of truck. At this time, the truck has traveled 1/4, and the distance from the meeting point is 4/9- 1/4=7/36, so the whole journey = 28/(7/36) = 16.

3. Party A and Party B walk around the city, with Party A walking 8 kilometers per hour and Party B walking 6 kilometers per hour. Now both of them start from the same place at the same time. After B meets A, it will take another 4 hours to return to the original starting point. B How long does it take to go around the city?

Solution: The speed ratio of Party A and Party B = 8: 6 = 4: 3. When meeting, Party B did 3/7 of the whole journey.

Then 4 hours is 4/7 of the whole trip.

Therefore, the time spent on line B in a week =4/(4/7)=7 hours.

3. Question and answer of Olympic Mathematics in the fifth grade of primary school

1, car A and car B travel in the opposite direction along the expressway from station A and bilibili respectively. It is known that the speed of car A is 1.5 times that of car B, and the time for car A and car B to arrive at station C is 5: 00 and 16: 00 respectively. When did the two cars meet? Solution: It takes 16-5 = 1 1 (hours) for a car to get to station C ... When the second car is driving at 1 1, it takes1.

An express train and a local train are in the opposite direction. The length of the express train is 280 meters and the length of the local train is 385 meters. The time for people sitting on the express train to see the slow train pass is 1 1 sec, so how many seconds does it take for people sitting on the slow train to see the express train pass?

Solution: The speed at which people on the express train see the local train is the same as the speed at which people on the local train see the express train, so the ratio of the length of the two cars is equal to the ratio of the time when the two cars pass by, so the required time is 1 1.

3. Party A and Party B practice running. If Party A lets Party B run 10 meter first, Party A can catch up with Party B after running for 5 seconds. If B runs 2 seconds ahead of A, A can catch up with B in 4 seconds. Q: How many meters do two people run per second?

Solution: The speed difference between Party A and Party B is 10/5=2.

The speed ratio is (4+2): 4 = 6: 4.

So A runs 6 meters per second and B runs 4 meters per second.

4. Question and answer of Olympic Mathematics in the fifth grade of primary school

1, Xiaoming took part in six tests, and the average score of the third and fourth tests was 2 points higher than the previous two tests and 2 points lower than the latter two tests. If the average score of the last three times is 3 points higher than the previous three times, how many points is the fourth time higher than the third time? Solution: The third and fourth scores are 4 points more than the first two scores, 4 points less than the last two scores, and the last two scores are 8 points more than the first two scores. Because the sum of the last three times is 9 points more than the sum of the first three times, the fourth time is 9-8 = 1 (points) more than the third time.

Mom goes to the grocery store every four days and the department store every five days. How many times does mom go to these two stores every week on average? (expressed in decimal)

Solution: Walk 9 times every 20 days, 9÷20×7=3. 15 (times).

3. The ratio of the average of b and c to a is 13∶7. Find the ratio of the average value of a, b and c to a. ..

Solution: If the number of A is 7, then the number of B and C is * * * 13× 2 = 26 (copies).

So the average value of a, b and c is (26+7)/3= 1 1 (copies).

So the ratio of the average of A, B, C and A is 1 1: 7.

5. Question and answer of Olympic Mathematics in the fifth grade of primary school

1, 765 × 2 13 ÷ 27+765 × 327 ÷ 27 solution: the original formula = 765 ÷ 27 × (213+327) = 765 ÷ 27.

2、(9999+9997+…+900 1)-( 1+3+…+999)

Solution: Original formula = (9999-999)+(9997-997)+(9995-995)+...+(9001-1)

=9000+9000+……。 +9000(500 9000)

=4500000

3、 1998 1999× 1999 1998- 1998 1998× 1999 1999