How many square meters is one cent of land? How many square meters is that nine?

One hectare is ten thousand square meters, one hectare is fifteen mu, and one mu is ten. So one cent is about 66.7 square meters, and nine percent is about 600 square meters

Find a solid metal ball, use the spring dynamometer to measure the gravity in the air is 89 n, immerse it in the water, the indication of the spring scale becomes 79 n, find: (g = 10N / kg)
1. What is the buoyancy of the metal ball? 2. What is the volume of the metal ball? 3. What metal is the ball made of?

(1) The buoyancy of metal block: F floating = G-F pulling = 89n-79n = 10N (2) volume of metal block expelling liquid: V row = f floating / PG = 10N / 1.0 × 103kg / m3 × 10N / kg = 1 × 10-3m3 (3) mass of metal block: M = g / g = 89n / 10N / kg = 8.9kg density of metal block: ρ ball = m / v = 8.9kg / 1 × 10-3

It is known that the length of the hypotenuse of a right triangle is C, and the lengths of the two right angles are a and B (a) respectively

a^2+b^2=c^2
b^2=ac
a^2+ac=c^2
Divide both sides by C ^ 2
(a/c)^2+a/c=1
A / C = (root 5-1) / 2

Two pieces of wood a and B with mass of M1 and M2 are stacked on a smooth horizontal plane,
A. The dynamic friction coefficient of B is u. if B is pulled out from the upper surface of a, the horizontal tension applied to B is (sliding friction = maximum static friction)

(F-um2g)/m2 > um2g/m1
So f > Um2 ^ 2G / M1 + um2g

If the base period is negative and the end period is positive, how can we calculate the positive growth rate and the negative growth rate?
For example, if the opening balance is "negative 20" and the closing balance is "positive 200", how to calculate the growth rate?

Increase = 200 - (- 20) = 220
Growth ratio = 220 / 20 = 1100%

A car braked at an acceleration of 2m / S2 to make a uniform deceleration linear motion, and the displacement it passed in the last 1s before it stopped moving is______ ．

If the motion of a car is regarded as a uniform acceleration motion with zero initial velocity in the opposite direction, the displacement of the car passing through in the last 1s after braking is reverse, and the displacement in the first second of uniform acceleration motion with zero initial velocity is x = 12at2 = 12 × 2 × 12m = 1m, so the answer is: 1m

What is A3 equal to if the first n terms of the urgent known sequence {an} and Sn = 3N + 4
urgent

a3=3

The vehicle starts to move at an acceleration of 1m / S2 from standstill. What is the average speed of the vehicle in the second second second? What is the displacement?

∵ the first second displacement X1 = v0t + 1 / 2at ^ 2 = 0 + 1 / 2 * 1 * 1 = 1 / 2m
Displacement in the first 2 seconds x2 = v0t + 1 / 2at ^ 2 = 0 + 1 * 2 = 2m
The second second second displacement = 2-0.5 = 1.5m
The average speed in the second second is 1.5 / 1 = 1.5 m / s

Xiao Ming and Xiao Hua Run on a 400 meter circular track. Xiao Ming runs 5 meters per second, and Xiao Hua runs 4 meters per second
How long does it take for the two to meet for the first time?
If you want a formula, give more points

At the same time and in the same direction, it is the problem of pursuit
When they met for the first time, Xiao Ming just ran one more lap than Xiao Hua
Required: 400 ÷ (5-4) = 400 seconds

1. The original price of a piece of soap is 2 yuan per piece. If you buy more than 2 pieces of soap, the mall will offer two kinds of preferential measures: one is the original price, and the rest is 70% off; the other is 20% off. In the case of purchasing the same quantity, how many pieces of soap do you need to buy if the first one is more cost-effective than the second one?
2. A student wants to buy a high school supplies. The initial price of the supplies in stores a and B is a yuan. Later, the student found that the current price of the supplies in store a is still a yuan, but the current price of store B is 10% higher than the original price of a yuan. Please help the student choose which store to buy the school supplies
3. 23 students from class 2, grade 1 of Yuying middle school go to the park on Sunday. The ticket window of the park shows that the ticket price is 10 yuan per person and 20% discount for group tickets for more than 25 people. What do you think is the most favorable way for these 23 students to buy tickets?
4. During the festival, a notebook in the stationery shop is on sale at a 20% discount. A student found that there are two of the same notebooks. During the festival, it's just 0.1 yuan less than before the festival. How much is the price of this notebook before the festival
5. Ms. Wang's favorite products are sold at the same price in shopping malls A and B. the promotion methods of the two shopping malls are different: when shopping in shopping malls a for more than 100 yuan at one time, 20% discount will be given to those more than 100 yuan; when shopping in shopping malls B for more than 50 yuan at one time, 10% discount will be given to those more than 50 yuan. How much discount will he get when shopping in shopping malls a be the same as when shopping in shopping malls B?
Please forgive me if there are any mistakes! We are studying practical problems and linear equation 4 in the first volume of junior high school!

1 2+0.7(x-1)

How many square meters is one cent of land? How many square meters is that nine?