Sixth grade math calculation problems (the more difficult the twenty problems, the better)

1, Master Wang processed a batch of parts. The original plan is to process 30 parts per hour, which can be completed in 6 hours. In fact, more parts are processed per hour than originally planned.

20%, the actual processing of these parts is several hours ahead of schedule.

2. A cylindrical oil drum with an inner diameter of 40 cm at the bottom and a height of 50 cm. If the diesel oil weighs 0.85 kg per cubic decimeter, this oil

How many kilograms of diesel can a barrel hold?

3. Wang Fei traveled 3 kilometers per hour when going up the mountain, and returned from the original road when going down the mountain, traveling 6 kilometers per hour. Ask him for the average speed of going up and down the mountain.

The bus and truck run in opposite directions from the midpoint of A and B at the same time. Five hours later, the bus arrived at A and the truck returned from B.

It's 60 kilometers. It is known that the speed ratio of trucks and buses is 5: 7. What is the distance between a and b?

application problem

1, 1 (day) 2,53.38 (kg) 3,4 (km) 4,420 (km)

1. Xiao Qiang and Xiaoming each have some money. As we all know, Xiao Qiang's money accounts for 60% of their total money. When Xiao Qiang lent Xiaoming 180 yuan, the ratio of money between Xiao Qiang and Xiaoming was 2:3. How much money do two people have?

2. Xiao Qiang climbs mountains. When climbing the mountain, his speed is 1.8 kilometers per hour. After reaching the top of the mountain, he immediately went down the mountain and returned to his original place. Walk 3 kilometers per hour when going downhill, and find the average speed of going back and forth.

3. Party A, Party B and Party C have cooperated with a number of parts. Party A made Party B 1/2, Party B made Party A and Party C 1/3, and Party C made 250 pieces. How many parts are there in this batch? 1. Xiao Qiang and Xiaoming each have some money. As we all know, Xiao Qiang's money accounts for 60% of their total money. When Xiao Qiang lent Xiaoming 180 yuan, the ratio of money between Xiao Qiang and Xiaoming was 2:3. How much money do two people have?

Now Xiao Qiang's money accounts for the sum of their money.

2÷(2+3)=2/5

Two people * * * have

180 ÷ (60%-2/5) = 900 yuan.

Let the uphill distance be 1.

Then the climbing time is 1÷ 1.8.

The downhill time is 1÷3.

The average round-trip speed is1× 2 ÷ (1÷1.8+1÷ 3) = 2.25 (km/h).

What a did was complete.

1÷( 1+2)= 1/3

What b did was complete.

1÷( 1+3)= 1/4