For a primary school math problem, the calculation process should be calculated, not with junior hig

Draw a line diagram and take a look.

Take the distance of A and B as the whole process.

The two cars met for the first time and traveled for 1 whole journey.

Of these, A traveled 40 kilometers.

The two cars met for the second time, and a total of 3 full journeys.

A traveled 1 full journey plus 20 kilometers.

The two vehicles travel 3 times in total, and the time spent on 1 trip is 3 times that of 1 full journey.

A should work: 40 3 = 120 km.

That is, 1 whole journey plus 20 km equals 120 km.

Distance between A and B: 120-20=100 km.

The two cars meet for the third time, and a total of 2 3-1 = 5 full journeys.

A line: 40 5 = 200 km.

A traveled exactly 2 whole journeys and returned to A.

So the third time the two cars will meet in the first place.

Hello: Pre-set: A speed: v1 B speed: v2 The first encounter is from B: x1 The second encounter is from A: x2

1) Calculation: 1 formula: v1 * ti = 40 2 formula: v2 * t1 = x

Three-form: v1*(t1+t2)=(40+x)+20 Four-form: v2*(t1+t2)=(40+x)+(40+x)-20

Formula 2: v1 v2=40 x 3 formula: 4 formula: v1 v2=(60+x) (60+2x).

Then there are the above two formulas: x2-20x-2400=0 x=60 so the distance between the two places: 60+40=100 (meters).

2) Calculation: by v1 v2=40 x=40 60=2 3 The speed is unchanged: so t1=t2=t3 Total distance: 100*2 meters.

Therefore: from place B: [-20+100*2 (3 5)] 100=80 (m) So the third meeting is 80 meters away from place B (or 20 meters from A).

a:：40×3=120

B: Adi. I'm not sure about that, after all, I'm only in the fifth grade......

Elementary school math formulas about proportionality:

Distance: Time = speed (certain), distance and time are proportional.

Workload: Working time = work efficiency (certain), workload and working time base type are proportional.

Total price: quantity = unit price (certain), the total price is proportional to the quantity.

The distance on the diagram is disproportionate: the actual distance = scale bar (certain), and the distance on the diagram and the actual distance are proportional to the bucket pin.

Characteristics of proportionality:

1. When the value of x in the inverse proportion, the value of the independent variable is also converted into its reciprocal, and the inverse proportion is transformed into positive proportionality. When the value of x in a positive proportion (the value of the independent variable) is converted to its reciprocal, the positive proportion is converted to an inverse proportion.

2. The proportional image is on a ray that passes through the origin. It is from the intersection of the abscissa and ordinate of the statistical table along the diagonal line from the lower left corner to the upper right corner, extending to the outside of **, where it can extend downward in the sense of proportionality, so it is considered a straight line.

Connected BE, the area of the large triangle is divided into 2:3, and the area of ΔADE is half of ABE, so the area of ADE is 1 3 times that of BCE, which is 12x15 (2x3)=30cm2

Connect the dot cd with a dotted line. Triangle ACD=1 2 ABC, AED=1 3 ACD, AED=1 6 ABC=12*25*1 2*1 6=25 square centimeters.

1, 2 car relative speed.

The length of time that the person sitting on the fast train sees the slow train passing = 385 11 = 35 (meters and seconds).

The person sitting on the slow train sees the time when the fast train passes.

The length of the express train is relative to the speed.

8 (seconds) 2, 9 and 6/7 + 99 and 6/7 + 999 and 6/7 + 3/7 = 9 + 6/7 + 99 + 6/7 + 999 + 6/7 + 1/7 + 1/7 + 1/7 + 1/7

9+ (6/7 + 1/7) + 99+ (6/7 + 1/7) + 999+ (6/7 + 1/7).

Questions for elementary school students? Oh my God, it's so hard, I didn't even understand the question, miserable, I doubt my IQ!

2 ( 9 6 7 1 7) ( 99 6 7 1 7) (999 6 7 1 7).

1 8 seconds The person sitting on the fast train sees the slow train passing by for 11 seconds, and one fast train and one slow train are moving opposite each other, so the sum of the speeds of the two cars is (385 280) 11 35 m s.

The time when a person sitting on a slow train sees an express train passing is when two cars drive together, and the length of the fast train is 280 35 8 seconds.

Ah! Looks like I'm going back to kindergarten to repeat - no!!

The first question is also 11 seconds, the person sitting on the slow train sees the fast car passing by, which is equivalent to the person sitting on the fast train seeing the slow train passing by, and I can't do it in the second question.

Second.

99 + 999 + 3 = 1110 (because the fractions add up to exactly 3).

About seconds! Second: 999 99 9 3 and 6/7 7 3 = 1107 3 and 6/7 3/7 3/7 = 1111 2/7

Break 1225 into prime factors:

From the above decomposition of the prime factors can be seen:

The circumference of the square is: 35 4 = 140 (cm).

The circumference of the rectangle is: (25+49) 2=148 (cm) or (5+245) 2=500 (cm) or (175+7) 2=364 (cm).

It can be seen that the circumference of the rectangle must be greater than the circumference of the square.

As for the circle, although its area is similar to a rectangle with a length of half a circumference and a width of the radius, it involves pi (, not an integer, and cannot be decomposed normally by prime factors, you must study the fourth unit (circle) of the first volume of the sixth grade before you can solve it.

1225 = 35 * 35, so the side length of the square is 35, and the circumference is 35 * 4 = 1440 cm.

1225 = 245 * 5 = 175 * 7 + 1225 * 1, so the maximum circumference is (1225 + 1) * 2 = 2452 cm.

1256=, so its radius is 20 centimeters, and its circumference is the longest circumference of a centimeter rectangle and the smallest circumference of a circle.

If the area is equal, the circumference of the rectangle is the largest, the square is second, and the circle is the smallest.

I don't, but I can help you ask my teacher, and I'll tell you later!

The circumference of the circle is the smallest and the rectangle is the largest.

Calculate the length of the square first, and then calculate the circumference.

Then calculate the radius of the circle and calculate the circumference.

Which one is smaller than that week.

Square open square x4 Park 1256 open square x2x rectangle is not easy to say, less than 1225 is OK.

1225=35*35

Square side length: 35 cm.

Square circumference: 35 4 = 140 (cm).

Rectangle length: 175 cm Width: 7 cm.

The circumference of the rectangle: (175+7) 2=182 2=364 (cm) This is the shortest circumference (because length and width are the closest).

Radius of the circle: 20 cm.

The circumference of the circle: 20-2 cm).

So the circumference of the rectangle is the largest, and the circumference of the circle is the smallest.

If the area of the three graphs is equal.

then the circumference of the rectangle is the circumference of the square and the circumference of the circle.

The circumference of a circle is the smallest, followed by a square, and the rectangle is the largest.

This question calculates the circumference of a circle and the circumference of a square, respectively.

For the same perimeter, the area of the square is greater than the area of the rectangle.

1/2+1/4+1/6+1/12+1/20+1/30+1/42+1/56

Simply put, it's a list of items and then just erases.

1 2 1 12 does not count first.

1 1 8 This is mainly the general and the approximate of use.

The distinction of different fractions of the denominator into a fraction of the same denominator that is equal to the original is called a general fraction, and a fraction is transformed into a fraction that is equal to it, but the numerator and denominator are relatively small, which is called a fraction.

1/6=1/2-1/3 1/12=1/3-1/4 1/20=1/4-1/5 1/30=1/5-1/6 1/42=1/6-1/7

Then replace these equations and it will become 1 2 + 1 4 + (1 2-1 3) + (1 3-1 4) + (1 4-1 5) + (1 5-1 6 ) + 1 6-1 7) + (1 7-1 8).

Then reverse the order and recombine the numbers that cancel each other up to 1 2 + 1 2 + 1 4 + (1 3-1 3) + (1 4-1 4) + (1 5-1 5) + (1 6-1 6) + (1 7-1 7) -1 8

Split the denominator separately, 6 = 2 x 3, 12 = 3x4, 20 = 4x5, 30 = 5x6, 42 = 6x7, 56 = 7x8, then, 6 = (1/2) - (1/3), 1/12 = (1/3) - (1/4), 1/20 = (1/4) - (1/5), 1/30 = (1/5) - (1/6), 1/42 = (1/6) - (1/7), 1/56 =(1/7)-(1/8);Next, go to scratch and merge.

Equals, three-quarters + one-half - one-third + one-third - quarter + quarter - fifth +. Plus one-seventh-one-eighth = five-fourth-eighths = nine-eighths.

Assuming that each hit 7 shots, A scores 7*4-3*2 22 points, and B scores 7*5-3*3 26 points.

A is 4 points smaller than B, and the actual A is 10 points more than B, and the difference between the two is 14 points to adjust the number of hits:

If A is added by 1 and B is reduced by 1, then A's score will increase by 2+4 6, B will decrease by 3+5 8, and the score gap will be reduced by 14 points. Exactly in line.

So 8 in A and 6 in B

Consider 10 shots in the first 10 rounds, and score 10 4=40;Then 4 shots in B, the score is 4 5-3 6 = 2, and the difference between the two is 38 points.

Considering that A is less than one shot, the score is less 4+2=6;B hits one more shot, and the score is 5+3=8, and the gap is reduced by 14 points.

In fact, A has 10 points more than B, and 28 points must be adjusted, that is, two shots.

The result was 8 shots in A and 6 shots in B.

If 10 shots are hit, 40 points are awarded.

Then 4 shots in B get 2 points, a difference of 34 points.

If the first hit 9 shots, 34 points are awarded.

Then 5 shots in B get 10 points, a difference of 24 points.

If the first 8 shots are made, 28 points are awarded.

Then 6 shots in B get 18 points, a difference of 10 points.

So 8 shots in A and 6 shots in B.

Solution: Let X hair in A and Y hair in B.

x+y=14

4x-2(10-x)=5y-3(10-y)+10 gives x=8, y=6

The ratio of the area of the circle to the area of the first square is:

The ratio to the area of the second square is: 4*2::

The ratio to the area of the third square is: 8*2::

The ratio of the area of the circle to the area of the sixth square is: 16*2*2*2::

Note: (: stands for "than" * for "multiplication".

(1) r: s = 4 (r: circle area s: square area) (2) r: s = 8

3) r ：s =π4*(2*2)) 16(4) r ：s = 4*(2*2*2*2*2)) 128

1800=2*2*5*5*3*3*2

Guess what, probably.

A highway with a total of 3,600 meters, has two engineering teams, A and B, who are building this road in opposite directions at the same time, and the speed of A is 350 meters and B is 250 meters. Q: How many hours does it take to complete the road?

There is no process, this can only be done with shaving.