Oral grouping

1, integer+number divided by integer ten or hundred.

(1) Calculate division and want to multiply; For example, 60÷30= () can be considered as (2)*30=60.

(2) Calculated by division in the table. Use the nature of division operation: expand or shrink the dividend and divisor by the same multiple at the same time, and the quotient remains unchanged. For example, if 200÷50 wants 20÷5=4, then 200÷50=4.

2. Estimation method of dividing two digits by two digits or three digits: Division estimation is generally to "round" the numbers in the formula that are not integer ten or hundred into integer ten or hundred, and then perform oral calculation. Note that the results are marked with √.

(b) Written division of labour

1, divisor is a two-digit pen division calculation method: divide the first two digits of the dividend by the divisor first, and if the first two digits are less than the divisor, look at the first three digits. Except for the dividend, the merchants wrote it on that. The remainder after each division operation must be less than the divisor.

2. Trial-and-error method of two-digit division in which the divisor is not an integer: If the divisor is a two-digit number close to an integer, the divisor can be regarded as the trial quotient of the integer close to it by rounding, or the divisor can be regarded as the number fifteen close to it, and then the quotient can be directly determined by multiplying one digit.

Second, the application of division

One day, when the digital cards were having lunch together, the youngest one spoke. Brother 0 said, "Let's take some photos together. What do you think? " 0' s brothers and sisters said in unison, "Good." Brother 8 said, "Brother 0' s idea is really good. I will be a good person once. Shall I provide camera and film for Brother 8? " Old four said, "starling, yes, it's just a little troublesome." Better use my digital camera. That's settled. " "Yes, they are very busy. Finally, the+sign took it for them, and they immediately sent the digital camera to the print shop. Computer sister wants to ask them for money, but who will pay? They stared at each other one after another. This is what the computer sister said, "A ***5 yuan, a * * * eleven brothers and sisters, how much does one person pay on average?" Among the eleven of them, Lao Liu is the cleverest, and this time he is the first to work out the result. Do you know how it is worked out?

Analysis: A * * * needs to pay 5 yuan, and there are 1 1 brothers and sisters respectively. Therefore, applying the concept of division, we get 5÷ 1 1≈0.454545 ... which is inexhaustible, so we estimate it as 0.45 by rounding.