Primary School Mathematics Olympiad Questions Challenging Intelligence Primary School Mathematics

The first is obviously not going to work. The first is equivalent to a car driving 3 times (send it over, drive back, send it back again) on a distance of 15 km, which is obviously not enough time for 60 (15*3) and takes 45 minutes.

Whether the second method is feasible depends on how much the second group of people can get out. The speed of the car is 60 kilometers per hour, in other words, 1 kilometer per minute, then 42 minutes can only travel 42km at most, and the first time the first group of people is sent to travel 15km, so the total distance of returning plus sending the second group of people can only be 42-15 = 27 at most, that is, the second group of people only needs to walk 15-27 2 = before the car meets them. So whether the car can go before it meets the second group of people is to calculate the total time it takes for the car to send the first group of people and then return to meet the second group of people.

Time = 15 (time for the first group of people to arrive at the airport) + time for the return to meet the second group of people) = minutes. During this time, the distance traveled by the second group of people is that this number is definitely larger, so they will definitely be able to complete the task in 42 minutes.

Scenario 1: 15 60=1 4, i.e. 15 minutes.

It was also 15 minutes to return and 15 minutes to go back for the second transport, so it was not possible to get in time.

Scheme 2: 15 60 = 1 4, that is, 15 minutes, the remaining three people, 15 minutes to walk the kilometer, the distance is left.

Hours 13 minutes.

On the return trip of the car, the remaining three people walked again: kilometers.

Minutes Left.

Total time: 15 + 13 + 13 = 41 minutes.

Option 2: Can be arrived at the scheduled time.

3-4 hours.

45 minutes. 45 minutes was greater than 42 minutes, so it was not possible to arrive on time.

45-65 hours.

41 and 7/13 minutes, less than 42 minutes, the second option is feasible.

Can arrive on time.

If the first option is used, the car will have to make three trips, send four people to the airport, then return to the same place, and then pick up the rest to the airport, which will take a total of 45 minutes, and it will not be able to arrive.

With the second plan, it took 15 minutes to send the first group of people to the airport, the second group of people has walked kilometers, and if the car meets the second group of people after a few hours, then 5a + 60a = , a = 165 13 minutes, a < 13 minutes, so the time to send the second group of people to the airport is less than 26 minutes, 26 + 15 = 41<42, then the second plan can arrive within the specified time.

The first option:

60 60 1 (km min).

15*3 45 (km) 45 1 45 (min) 45 mins >> 42 mins Answer: The first option cannot be arrived within the specified time.

The second option:

15 60 hours) km).

Approximately equal to hours.

min) <42

A: The second option can be arrived within the specified time.

I'm sweating, it's been a long time ago, and I still remember it vividly, the first one (that is, waiting for the bus in place) is not good.

2) The scheme can, (1) the scheme cannot.

[Part 1].

Topic] Grandpa Zhang's age Grandpa Zhang, Ah Ming, and Xiaohong are 91 years old, and Ah Ming is known to be 22 years old, which is 2 times that of Xiaohong, how old is Grandpa Zhang? (30 minutes).

Topic] Flooded Ships.

There is a 10-meter-high boat parked on the beach, the sea water **, the average sea water per minute ** 1 meter, how many minutes does it take to submerge the boat?

How fast can you eat 15 cookies in a few minutes?

How fast can you eat 15 cookies in a few minutes?

There are 15 cookies. The first person ate 1 piece, divided the rest equally, and divided it among 2 people.

The two people who got the biscuits ate 1 piece of chai dan as before, and then divided it equally among the two people.

The time to eat 1 cookie is 1 minute, and the time to change hands in the middle is not counted.

There is no limit to the number of people who can eat cookies.

How fast can you eat these cookies in a few minutes?

Answer: These cookies can be eaten in as little as 4 minutes.

Topic: Jumping a big rope.

Allocation of dollars. A and B were hired by the farm to sow seeds, and each of the 10 acres of land was divided into half, and A began to work from the east and B from the west. It takes 20 minutes for A to clear an acre of land, but it takes 40 minutes for B, but B sows three times faster than A.

The salary is 100 US dollars, and he asks how to distribute the money, how much will B get?

Answer: B can get the letter to 50 US dollars.

[Part 2].

Change I went into a gift shop and saw a camera, which was worth 30,000 yen in Japan with a leather case, but the store cost 310 US dollars (US dollars, not Thai baht), which is equivalent to about 40,000 spikes and more yen. The price of a camera is $300 more expensive than a holster, and the rest is the price of a holster. Excuse me:

Buy a pair of leather cases and take out $100, how much change should I find?

Answer: If you don't think about it, you will be deceived. If the holster is $10, then the camera is $300 more expensive, or $310.

That adds up to $320. The correct answer should be $5 for a holster and $95 for change. In this way, the camera is $305 and the holster is $310 for a total to qualify for the calculation.

Title] Coconut Tree.

There was a tall coconut tree, and monkeys, orangutans and bears came and said who could climb the tree the fastest and pick a banana?

Topic] Subtraction.

Subtract 15 from 100 each time and add 10, how many times will 100 be subtracted exactly after that?

Topic] Little snails.

The baby snail climbs up from a 7-meter deep hole, and every time it climbs 3 meters, it has to slide down 1 meter, how many times does it climb to climb up to the hole?

Count out who lied.

There are 3 people playing a game of nervous breakdown with 10 sets of 20* cards.

A: "I hit up to 10 times in a row".

b: "I hit up to 9 times in a row".

C: "I hit up to 8 times in a row".

There is a man who lies, who is it?

Answer: b "I hit up to 9 times in a row".

The original question was answered correctly.

20 minutes in advance, it actually takes time for the car to walk to and from the student's walking distance.

In other words, it takes 10 minutes for students to walk by car.

It's hard to understand why students walk for 50 minutes.

Students depart 1 hour in advance, but the actual meeting time between the car and the student is 8:50 (10 minutes before 9 a.m.).

So, the student's walking time is 50 minutes.

So: v car: v student = 5:1 v student = 48 5 = kilometers per hour) as shown in the figure below: the timetable of the car and the student respectively, it may be easier to understand after reading it.

The answer is correct.

The bus arrived at its destination 20 minutes early, which would have been spent on the journey to and from the students. So that means it only takes 10 minutes for the car to cover the part of the road that the students have already walked. Then it took the students 50 minutes to walk, because the car arrived on time at 9 o'clock, and now it saves 20 minutes, because it is a round trip, so it saves 10 minutes in one trip, that is to say, the car meets the students at 8:50, and the students have walked for 50 minutes, so the ratio of the speed of the car to the students is 5:

1, so the student's speed is 48 divided by 5

You can draw a diagram, you can see very clearly, the distance the student walks, the car needs to go twice, assuming that the school is A, the destination is B, the place where the middle meets is C, the student's road is AC, the car is BC, if the car is going to go to A according to the original plan, and then go back from A, so this part of the AC road is supposed to go twice. But your solution is also wrong.

The time ratio is 60:10

So the speed ratio is also 6:1

So the student speed should be 48 6 = 8km hour.