Examples of the one way forward and one way back in elementary school mathematics

Advance method - when the approximate value of the interception number is removed, the rounded part is removed, and 1 is added to the last digit of the reserved part, and this method of approximating the interception number is called the advance method. For example, use = to the percentile.

, the approximation is .

Tail removal method - when the approximate value of the interception number is removed, the rounded part is removed, and the number retained remains unchanged, and this method of approximating the interception number is called the tail removal method. For example, the value of = when truncated to the thousandth with the detailing method is.

Here's an example

For example, a sack can hold 200 catties of wheat, and there are 880 catties of wheat, and several sacks are needed to fill it.

Divide 880 by 200, the quotient is 4, the remainder.

is 80, even if it is impossible to use 4 sacks, it must be completed with 5 sacks by the method of progression.

One way forward" and "one way back". For example, 288 students go on a spring outing, and 45 people have a bus, which is a bus, but you must enter one to not let people come out, not to let the car be less, not to let the car become a decimal, then you need 7 buses. For example, 1016 liters of gasoline, to refuel the car, 20 liters of one, the average can be added, but you must return one to not let the car out, let the fuel less, do not let the car become a decimal, you can refuel 50 cars.

One method: 1. There are a total of 37 kilograms of beverages, and each bottle contains 4 kilograms, how many bottles do you need to fill them all?

2. The teacher took 32 students to row, and only 5 people can sit in each boat, how many boats do they need to rent to sit down?

3. The zoo is going to move, and there is a cage for every 6 monkeys, and now there are a total of 38 monkeys, how many cages are needed?

Tail removal method (one retreat method):

4. My mother bought 20 meters of cloth, and I can make a set of clothes every 3 meters, and how many sets can I make at most?

5. A bag of plum is 6 yuan, so how many bags can you buy for 50 yuan?

6. There is a rope 55 meters long, and a long skipping rope can be made every 7 meters, how many long skipping ropes can be made at most?

For example, if you calculate that you need to buy a bag of cold powder, but when you can buy it, you can only buy 8 bags, and half a bag of medicine is not sold in pharmacies, which is what it means.

Rounding is not the same as rounding. The method of advancing is to add one to the decimal part, no matter how many it is.

For example, 70 divided by 80 equals approximately 1

"Advance one" should be to reach the condition of the previous single digit, and then move forward one.

They all said it better, so I won't explain it.

Are you talking about abacus? Or something else?

The method of advancement is to remove the number of the excess part and add 1 to the last number of the reserved part. The resulting approximation is an excess approximation (i.e., greater than the exact value). When rounding up with the method of into, which digit is rounded to, no matter how many numbers are in the next digit, as long as the following digits are not all 0, advance one to this digit, and then rewrite the numbers after this digit to 0.

Example: A sack can hold 200 catties of wheat, and there are 880 catties of wheat, how many sacks do you need to fill it? Divide 880 by 200, the quotient is 4, and the remainder is 80, that is, it is impossible to use 4 sacks, so it is necessary to use the further method to use 5 sacks to finish.

The tail removal method is a common mathematical method of removing the decimal part of a number and taking its integer part, and the value is an approximate value (smaller than the exact value), which is often used in life. It is also called the tail removal principle.

Example: Use cloth for each piece of children's clothing2 meters, the existing cloth rice, ask how much you can make such clothes.

Solution: 17 6÷

The result was 14 66……, if the approximate value is rounded, then 15 pieces should be obtained. But when it comes to making clothes, everyone understands that although the rest of the cloth can be made into a piece, it is not enough to make a piece of cloth, so it can only be done by removing the tail. Namely.

A: 14 pieces of such clothes can be made.

The method of advancing is to omit the digit, no matter whether his number is greater than five or less than five, he must be rounded up to move forward one place, the district committee method is the decimal point, and the following digits are omitted for him!

The method of removing the tail is to leave the omitted position regardless of whether it is full of five or not. For example, there are 25 meters of cloth, and each set of children's clothes needs to be made with cloth and each set of cloth rice, how many sets can be made in total? So how many sets can be made is 25 sets, according to the convention is to give equal to 12 sets, but the remaining mantissa is not a set at all, so it can only be used to remove the tail method to equal to 11 sets.

The method of advancing one is that as long as the omitted bit is greater than zero, one place must be advanced. For example, if you have 101 liters of oil and need to pack them in small oil drums with a volume of 20 liters, how many small oil drums do you need? With 101 20 = small oil drums.

Conventional rounding is approximately equal to 5 small oil drums. But in fact, what is needed is 6 small oil barrels, because the remaining point also needs a small oil barrel, so it should be equal to 6 small oil barrels is used in one method.

Progressive:

For example, if you have litres of oil, each drum can hold 1 litre.

Q: You need at least a few oil drums to fill up.

Obviously, you can't pour that liter out.

So you're going to have to use 6 buckets.

Tail removal method: For example, if you have 580 points, you can exchange 1 prize for every 200 points.

Then you can theoretically exchange it for a prize.

But in fact, only 2 can be changed.

The method of advancement is to add l before the large number, removing all the numbers at the end, such as:

1. Further method:

The method of advancement is to remove the number of the excess part and add 1 to the last number of the reserved part. This results in an approximation that is larger than the exact value.

Example 1:; Example 2: A sack can hold 200 catties of wheat, and now 880 catties of wheat, how many sacks do you need to fill it?

880 200 4 (pcs) ......80 (jin).

4+1 5 (pcs).

A: It takes 5 sacks to fill it up.

2. Tail removal method:

The tail removal method is to remove the approximate value of the truncated number, after removing the rounded part, the number retained remains unchanged, so that the approximate value obtained is smaller than the exact value.

Example 1:; Example 2: Each piece of clothing needs to use 2 meters of cloth, and the existing cloth is 17 meters, how many pieces of such clothes can be made?

17 2 8 (pieces) ......1 (m).

A: You can make 8 pieces of such clothes.

Name? Name? Name? Name? Name?

Solution: The main methods of mathematical calculation to approximate the value are: "tail removal method", "advance method" and "rounding method".

The method of advancing refers to taking an approximate number and keeping an integer, regardless of the number in the decimal part of the decimal part

Advance to the integer part of the whole number.

The detailing method refers to taking an approximate number and keeping an integer, regardless of the number in the decimal part of the decimal part

The method of removing all of them.

In the specific problem of taking approximate numbers, rounding is generally used.

However, sometimes it is necessary to flexibly apply the tail removal method or the further method according to the different circumstances of the specific problem.

To advance a method is to advance a method.

If there is no non-zero number after zero, you don't need to enter, if there is a non-zero number after zero, for example, if the advance method is accurate to an integer, you need to enter one place, which is 4

As long as the obtained number is not an integer, the decimal part of the original number is removed, and the result is added by one.

Same: The results are all approximate. Differences: the result of the first method is larger than the original, and the result of the tail removal method is smaller than the original.

The next way is that everything with a decimal becomes the smallest integer larger than this decimal

The use of the method is generally not allowed to be used in the case of rounding, such as how many people need to move a certain thing within the specified time, if it is calculated to be a decimal number, such as, it is not in line with the facts, and rounding to 3 can not, it should be the need for people, 3 people are obviously not enough, so it is necessary for 4 people.