The distance between the school and the library is 18 kilometers. It took Xiao Ming 5 / 8 hours to get there, while Xiao Li 7 / 12 hours. Who is faster

The distance between the school and the library is 18 kilometers. It took Xiao Ming 5 / 8 hours to get there, while Xiao Li 7 / 12 hours. Who is faster

5 / 8 = 15 / 24 hours
7 / 12 = 14 / 24 hours
Xiao Li's time is short, so it's fast

The school library is 18 kilometers away. It takes Xiaoming 5 / 8 hours to get there, while Xiaoli 7 / 12 hours

5 / 8 = 15 / 24 hours
7 / 12 = 14 / 24 hours
15 / 24 hours > 14 / 24 hours
Xiaoli time period is relatively fast

It takes Xiaoli 12 minutes to walk from home to school. Every minute he walks from home to school (), 10 minutes (), half minutes ()

It took Xiaoli just 12 minutes to walk from home to school. He walked every minute (1 / 12) of the distance from home to school,
10 minutes walk (5 / 6)
Half a minute walk (1 / 24)
I wish you progress in your study, you can ask if you don't understand! Thank you!

（1/3+1/15+1/35+1/63+1/99+1/143）*80

（1/3+1/15+1/35+1/63+1/99+1/143）*80
=1/2*（1-1/3+1/3-1/5+1/5-1/7+.+1/11-1/13）*80
=40×【1-1/13】
=40×12/13
=480/13

On the calculation of pressure
4. A thin-walled cylindrical container with a weight of 3 N and a bottom area of 1 × 10-2 M2 contains water and is placed in the center of the horizontal table. If the mass of water in the container is 3 kg, the height of the container is known to be 50 cm. (G is 10 N / kg)
(1) The pressure of water in a container at a depth of 15 cm
(2) Pressure of container on table
(3) If an object with a volume of 3 × 10-3 m3 is immersed in the container, what is the pressure change of water on the bottom of the container?

(1) Pressure = water density * g * H = 1000kg / m ^ 3 * 10N / kg * 0.15m = 1500 Pascal
(2) P = (water mass * G + G container) / bottom area = 3300 Pascal
(3) After the object is immersed, the volume of water is equal, so theoretically, the water level rises as follows:
3 * 10 ^ - 3 / bottom area = 30cm
The original height of water is: water mass / water density / bottom area = 30cm
30 + 30 = 60 〉 50 excess water will overflow
So the pressure change is the density of water * water depth * g = 5000 Pascal
2000 Pascal more than before

Through point m (2.2), make a straight line l-intersection hyperbola x ^ 2-y ^ 2 / 4 = 1 in a, B two points m is the midpoint of AB, find l equation and ab length

Let a (x1, Y1) B (X2, Y2), any point on the line L (x, y) 4x1 & sup2; - Y1 & sup2; = 44x2 & sup2; - Y2 & su

How many resistors should 1N4007 diode be equipped with when it is used in 220 V voltage

See where you use, 1N4007 rectifier diode strong forward surge withstand capacity: 30A maximum average forward rectified current: 1A maximum reverse withstand voltage: 1200V low reverse leakage current: 5ua (maximum) forward voltage drop: 1.0V maximum reverse peak current: 30uA

Given the function FX = x & # 178; + 1 (x ≤ 0) - 2x (x > 0), if f (x) = 10, then x=

-3

What is the lighting range of 3-watt led? How many 3-watt LED energy-saving lamps should be installed in a 15 square meter room? Ensure the brightness!

15 square meters ~ one is enough

Then: a X-Y > = 0 B X-Y = 0 d x + y

Let f (T) = 2 ^ (T) - 3 ^ (- t)
F '(T) = 2 ^ (T) * in (2) - 3 ^ (- t) * in (1 / 3) > 0
Know the function increment;
There is also a question: F (x) > = f (- y)
So, x > = - Y
That is x + Y > = 0
Choose C