Mina, I urgently need 22 math application problems for the fourth grade of primary school, which chi

The master needs 4*6 processing. . . 24 hours.

Apprentice processing takes 24+6. . . 30 hours.

The apprentice processes 600 30 per hour... 20 pcs.

600 25 = 24 (hours) Master 1 shared 24 hours.

Then the apprentice will take 30 hours.

The speed of apprentice processing is 600 (24+6) = 20 (hours) Answer: The apprentice processes 20 parts per hour.

The total time for the master to process the parts.

Hour. The total processing time of the apprentice is as follows.

Hour. Number of apprentices processed per hour. Piece.

2249 110 21 (hours).

8 p.m. + 21 p.m. = 5 p.m. the next day.

Arrived at about 5 p.m. the next day.

2294 110 = 20 and 47 55 hours 20 hours 51 minutes.

20 hours 51 minutes - (12-8) 16 hours 51 minutes.

A: Arrive at 16:51 today.

2294 110 = 20 and 47 55 hours 20 hours 51 minutes.

20 hours 51 minutes + 20-24 = 16 hours and 51 minutes.

That is, today at 16:51.

Hello reduction = 16 13 - (16-1) (13-1) = 208 - 180 = 28 square meters.

or decrease = 16 1 + 13 1-1 1 = 28 square meters.

(1) Uncle Li's vegetable plot has a vegetable plot with a length of 16 meters and a width of 13 meters, and the area is: 16*13=208 square meters.

2) Now reduce the length and width of the vegetable plot by 1 meter each to build a road, and the remaining vegetable plot area:

16-1)*(13-1)=180 square meters.

3) How much has the area of the vegetable plot been reduced compared to the original? 208-180 = 28 square meters (4) comprehensive formula: 16 * 13 - (16-1) * (13-1) = 28 square meters.

Original area s=16*13=208

The present area s'=15*12=180

Reduce S-S'=208-180=28

The original area is 16*13=208

Now the area is 15*12=180

Reduction: (208-180) 208=17 52

10 99---90*2=180.

9 + 180 + 663 = 852.

10 19---1.

20 29--- 11.

30 39---1 pcs.

90 99---1 pcs.

Therefore, 1 99 is a total of 20.

100 199---20.

200 299---100 + 20 = 120.

300 320---3.

A total of 20 + 20 + 120 + 3 = 163.

1.(1) On pages 1 to 9, there are 9 numbers, 2) on pages 10 to 99, there are 99-10 + 1 = 90 (pages) there are 90 2 = 180 numbers, 3) 100 to 320 pages, there are 320-100 + 1 = 221 (pages), there are 221 3 = 663 numbers, 4) the page numbers for the compilation and printing of the book are 9 + 180 + 663 = 852 numbers.

2.Add 0 to 320 to make it all three digits: 000,001,002,。。 010，011,012.。。320

From 000 to 299, there are 0,1,2 in the hundred place, there are 100 2s, there are 300 10 = 30 2s in the ten digits (every 10 in a cycle), there are 300 10 = 30 2 in the single place, 300 to 320 have 302,312,320 in a total of 3 2s, a total of 100 + 30 + 30 + 3 = 163 (pieces) 2

Question type: Enumeration method to solve the problem.

pages.

1+2+3+..320 = 51360 pages 2 in single digit 2, 12, 22, 32, 42, 52, 62, 72, 82, 92, ten.

102,112...192 and ten, 202--- 292 ten.

302, 312 two.

2 in the tenths 20, 21, 22, 23, 24, 25, 26, 27--- 29.

120---129 ten.

220---229 ten.

320 a.

2 in the hundredth 100.

Total 32 + 31 + 100 = 163

1 to 9: 9 numbers are required.

10 to 99: 90*2=180 digits are required.

100 to 320: 221 * 3 = 663 numbers are required: 9 + 180 + 663 = 852 (pieces) 1 to 100 The number 2 appears 10 times in the single digit and 10 times in the tenth digit, for a total of 20 times.

The number 2 from 101 to 320 appears 22 times in the single digit, 21 times in the 100 digit, and 100 times in the 100 digit.

A total of 20 + 22 + 21 + 100 = 163 times.

There are 9 10 99 and 2 * 90 = 180.

100 320 has 3 * 221 = 663.

There are 9 + 180 + 663 = 852 numbers.

There is 1 210-99 and 9 + 10 = 19 (the single digit is 2, and the ten digits can be taken as 1 9;The ten digits are 2, and the single digit can be 0 9).

100-320 has 30 + 30 + 100 = 160 (the single digit is 2, the ten digits can be taken 0 9, the hundred digits can be taken 1 3, there are 3 * 10; Ten digits are 2, single digits can take 0 9, 100 digits can take 1 3, there are 3 * 10; The hundred digits are 2, the single digit can take 0 9, the ten digits can take 0 9, there are 10 * 10)

There are 1+19+160=180 2s

, a total of 9*1=9 numbers; 10 99, a total of 90*2=180 numbers; 100 320, a total of 221 * 3 = 663 numbers. A total of 9 + 180 + 663 = 852 digits.

2.Single digit occurrence: 320 10 = 32 times, ten occurrences 320 10-1 = 31 times (1 9 no ten), 100 occurrences (299-200 + 1), a total of 32 + 31 + 100 = 163 times.

Because there is a 0 at the end, the number is equivalent to dividing by 10, which is ten times smaller and the two numbers are x y

x+y=685

x+y 10=460 x=435 y=250 or (685-460) (10-1)=25 is the number after ten fold reduction.

685-460=225

An add-on is 25*10=250

The other addition is 685-250=435

The total time for the master to process the parts.

600 25=24 hours.

The total processing time of the apprentice is as follows.

24+6=30 hours.

Number of apprentices processed per hour.

600 30=20.

600 25 = 24 hours Master needs 24 hours to complete.

24+6=30 hours It takes 30 hours for an apprentice to complete.

600 30 = 20 apprentices process 20 parts per hour.

The master needs 4*6 processing. . . 24 hours.

Apprentice processing takes 24+6. . . 30 hours.

The apprentice processes 600 30 per hour... 20 pcs.

25 600 24 (hours).

24 6) 600 20 (pcs).

So the apprentice processes 20 pieces per hour.