When father and son stand side by side in the swimming pool, father's height out of the water is 1 / 3 of his own height, son's height out of the water is 1 / 7 of his own height, and the sum of father and son's height is 3.2 meters

When father and son stand side by side in the swimming pool, father's height out of the water is 1 / 3 of his own height, son's height out of the water is 1 / 7 of his own height, and the sum of father and son's height is 3.2 meters

An iron bridge is 1000 meters long. A train passes through the bridge. It takes one minute for the train to get on the bridge and then completely cross the bridge. The time for the whole train to be completely on the bridge is 40 seconds (from the rear of the train to the front of the train about to get off the bridge). How about the speed and length of the train?

1 minute = 60 seconds, all pass: S1 = l bridge + L, T1 = 60s, all on the bridge: S2 = l bridge - L, T2 = 40s, let the speed of the train be v m / s, the length of the train be l m, then 60s × v = 1000m + l40s × v = 1000m − L, the solution is: v = 20m / s, l = 20m. That is, the length of the train is 200m, and the speed is 20m / s. answer: the speed of the train is 20m / S; the length is 200m

P is a point outside the square ABCD, Pb = 12cm, the area of triangle APB is 90cm & # 178; the area of triangle CPB is 48CM
Square centimeter, what is the area of square ABCD?

Let the side length of the square be a, and the heights of APB and CPB of the triangle be H1 and H2 respectively
Then 1 / 2 * a * H1 = 90 and 1 / 2 * a * h2 = 48
Because H1 ^ 2 + H2 ^ 2 = 12 ^ 2
There are (180 / a) ^ 2 + (96 / a) ^ 2 = 12 ^ 2 = 144
So a = 17

Given a + B = 2, find (A & # 178; - B & # 178;) - 8 (A & # 178; + B & # 178;)

Hello
(a²-b²)²-8(a²+b²)
=(a+b)²(a-b)²-8[(a+b)²-2ab]
=4(a-b)²-8[4-2ab]
=4(a-b)²+16ab-32
=4[(a-b)²+4ab]-32
=4(a+b)²-32
=16-32
=-16

What is the quotient of 3 divided by 72?
Question 2: 125x80, there are () zeros at the end of the product?
The third question: 150x90, the end of the product () 0?

It's 72 divided by 3, it's 24

The perimeter of a rectangle is 128 meters and its width is 25 meters. What is the area of the rectangle

Length + width = 128 / 2 = 64, so length = 64-25 = 39, so area = 25 * 39 = 975

Four fifths of 7 tons is () tons, () hectare is one third more than 48 hectare, () meter is two fifths less than 100 meter

Four fifths of 7 tons is (28 / 5) tons, (64) hectares is one third more than 48 hectares, (60) meters is two fifths less than 100 meters

If the train is 200 meters long, the time it takes for the train to pass through the 1000 meter long railway bridge is 30 minutes__ Seconds (20 m / s)

(1000 + 200) / 20 = 60 seconds

A rectangle is 3cm in length and 2cm in width. It rotates around its length and width axis to form two different cylinders. Which cylinder is bigger? How much

The volume of cylinder with length as height = 3.14 * 2 * 2 * 3 = 37.68 (CM & # 179;)
The volume of cylinder with width as height = 3.14 * 3 * 3 * 2 = 56.52 (CM & # 179;)
Therefore, the cylinder with the length as the height has a large volume, which is 56.52-37.68 = 18.84cm;

What are all integers in the statistical interval [10009999] that are divisible by 7 and the sum of thousands and ones is 7

To count this, these numbers only have the following format: 1xx6, 2xx5, 3xx4, 4xx3, 5xx2, 6xx1, 7xx01. The first one that can be divided by 7 is 1036, and the next one is 70 larger than the previous one, that is, 103611061176,. 1946. Similarly, the numbers starting with 2, 3, 4, 5, 6, 7 are as follows: 20652135205