To find the solution to the data problem in the third grade of primary school, you can only use addi

Chickens and rabbits in the same cage, a total of 120 feet, chickens and rabbits swapped a total of 96 feet, how many chickens and rabbits each?

Solution 1: Chickens and rabbits share: (120 96) (4 2) = 36 The number of chickens: (4x36-120) (4-2) = 12 The number of rabbits: 36-12 = 24

Solution 2: Chickens and rabbits share: (120 96) (4 2)=36 Rabbits are more than chickens: (120-96) (4-2)=12 Number of rabbits: (36 12) 2=24

Number of chickens: 24-12 = 12

Solution 3: There are more rabbits than chickens: (120-96) (4-2) = 12 The number of chickens: (120-12x4) (4 2) = 12 The number of rabbits: 12 12 = 24

Solution 4: Chickens and rabbits: (120 96) (4 2) = 36 The number of rabbits: (120-36x2) (4-2) = 24 The number of chickens: 36-24 = 12

If Xiaoliang is x years old this year, his father is x + 28 years old. Seven years later, Xiaoliang is x+7 years old, and Dad is x+28+7 years old, then there is x+28+7=(x+7)*3, and the solution is x=7, and Dad x+28=35 years old.

Dad 35 Xiao Liang 7

It should be estimated as a whole ten, 455-345 = ( ) 455 should be estimated as 460 or 450, and 345 as 340 or 350, so that the number is 100, which is very close to 105. I hope your son is doing well!

Rounding 4 and below is used to round 32 to 30, and 5 and 5 to 1 place, like 27 to 30

It is also possible to estimate the number as a whole ten, 455 as 460, 345 as 360, 460-360 = 100, 100 and 105 are very different.

Rounded to the nearest 0 for 4 and 4, and 10 for 5 and 5 above

For example, the above question approximates 345 to 350 and 455 to 460

Ah, what, it's so inaccurate, it's better to calculate accurately, otherwise it's useless to estimate during the exam.

Here's how to estimate it:

1. The method of rounding: such as making up a whole thousand, a whole hundred, and a whole ten.

2. Take an intermediate number: such as and 59 These four numbers are summed, these numbers are very close to 35, some are a little more than 55, some are a little less than 55, take an intermediate number 55, directly use 55 4, and roughly calculate the result of adding these numbers.

3. Estimate with special data characteristics: for example, 126 8, you can think of 125 8, 8 times of 125, and you can get 1000.

Rounding" method:

Look at one more digit than the reserved digit, the digit on the digit is "5" or greater than "5", forward one digit, the digit on the digit is "4" or less than "4", and round it off.

For example, keep one decimal place, that is. And, keep one decimal place, that is.

When taking a decimal approximation, if the highest digit of the mantissa is 4 or less than 4, remove the mantissa number. If the highest digit of the mantissa is 5 or greater than 5, round the mantissa to the position before it"1"This method of approximating numbers is called rounding.

The "rounding" method is also used in the Nine Chapters of Arithmetic, and when using the proportional method to find the vehicles that should be produced by each county, because the vehicles are whole numbers, they use the rounding method to deal with the calculation results.

Vertical step process analysis 382+137

Solution: The single digit of the two additions is aligned, and then the numbers on the same counting unit are added, and the addition result is 10 to the high position, and the high level needs to accumulate the result of the low position to 1.

Problem solving process: Step 1: 2+7=9

Step 2: 8+3=1 Advance 1 to the high position

Step 3: 3+1+1=5

According to the above calculation steps, the combined calculation result is 519

Estimate: 380 + 140 = 520

Addition du (1).

98+25= （zhi2）dao376+284= （3）135+48=

Subtraction back (1)517—348= (2)507—348= (3) 500—185=

Multiplication (1) 740

A: 6 (2) 209 9 (3) 540 5 (4) 804 9

Division (1)160 4 (2)450 5 (3)455 5=

Application Questions:1The experimental primary school has completed 130 meters of construction of a 400-meter-long circular plastic runway, and the rest will be completed in 30 days.

2.To celebrate New Year's Day, the students made 65 red flowers and 25 yellow flowers, and asked every 5 flowers to be tied into a bouquet, how many bouquets did the students make?

So 40-12-14 = 14, if you only add and subtract multiplication and radical division, 2 large is 10, and 4 small are 8, then 32 = 12 times wide 5-14 times 2, and 2 large = 5 small, I think like this: 1 large barrel is 3 kg more than a small barrel is very good to do with a binary equation, 14 = (2 + 5) times 2, so the value is 12 + 4 = 16

It should be estimated as a whole ten, 455-345=(, 455 should be estimated as 460 or 450, and 345 as 340 or 350, so that the number is 100, and the silver crack is very close to 105. I hope your son is doing well!