-1 / 2,2 / 3, - 3 / 4,4 / 5, - 5 / 6,7 / 8... Guess the sum of the nth number and the nth plus one number (n is odd)

-1 / 2,2 / 3, - 3 / 4,4 / 5, - 5 / 6,7 / 8... Guess the sum of the nth number and the nth plus one number (n is odd)

Sequence arrangement: numerator is item number, denominator is item number + 1, odd item is negative, even item is positive
N is odd, the sum of the nth number and the nth + 1 number = - N / (n + 1) + (n + 1) / (n + 2)
=[-n(n+2)+(n+1)²]/[(n+1)(n+2)]
=(-n²-2n+n²+2n+1)/[(n+1)(n+2)]
=1/[(n+1)(n+2)]
=1/(n+1) - 1/(n+2)

-12，23，-34，45，-56，67… Suppose that the sum of the nth number and the (n + 1) number (n is odd) is______ ．

The sum of the nth number and the (n + 1) number (n is odd) is - NN + 1 + N + 1n + 2 = 1 (n + 1) (n + 2). So the answer is: 1 (n + 1) (n + 2)

If the sum of any three numbers selected from 1, 2, 3, 4, 5, 6, 7, 8, and 9 is even, they have the same number______ There are two different choices

According to the stem analysis: 40 + 4 = 44 (species), a: there are 44 different choices

The inner straight channel is a 7-meter-high, 2-meter-65-centimeter-thick reservoir. I want to know how many cubic meters it will be built for settlement

So you mean to calculate the cube of the material, right? {(3.5 + 0.65) &# 178; * 3.14-3.5 & # 178; * 3.14} * 2 = 31.23

A cuboid reservoir, 5 meters long, 3 meters wide, 1.2 meters deep, to tile the bottom, how many meters need bricks. The thickness of the reservoir is 10 cm

Just tiling on the bottom?
What's the point?
It's great to directly multiply the length by the width
Just stick bricks. You can see clearly
5*3+2*3*1.2+2*5*1.2+2*3*0.1+2*5*0.1
=15+7.2+12+0.6+1
=35.8 (M2)

If the inlet pipe of a reservoir is filled with 8 cubic centimeters of water per hour, the empty reservoir can be filled with water in 6 hours
(1) Find the time t (H) required to fill the empty pool with water, and the function of Q (cubic centimeter) of water inflow per hour. (2) if the empty pool is to be filled with water within 5 hours, what is the water inflow per hour at least? (3) given that the maximum water inflow of the inlet pipe is 12 cubic meters per hour, how long does it take at least to fill the empty pool with water!

Solution (1): the volume of the reservoir is 8 × 6 = 48 cubic centimeter
t=48/Q
(2) When t = 5
48/Q=5
Q=48/5=9.6
If the empty tank is to be filled within 5 hours, the water inflow per hour should be at least 9.6 cubic centimeters
(3) : when q = 12
t=48/12=4
The maximum water intake is 12 cm3 / h, so it will take at least 4 hours to fill the empty tank

There is a cuboid reservoir on the roof, 8 meters long, 5 meters wide and 4 meters high. The water depth in the reservoir is 2 meters. How many cubic meters of water is there in the reservoir

Hello
8×5×2
=8×10
=80 cubic meters
A: this pool has 80 cubic meters of water
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A cylindrical pool, measured from the inside, has a bottom diameter of 20 meters and a depth of 4 meters. (1) what is the floor area of the pool? (2) How many cubic meters of soil are needed to dig this pool? (3) Put a layer of cement on the side and bottom of the pool, and use 0.5kg of cement per square meter. How much cement do you share?

(1) Floor area: 3.14 × (20 △ 2) 2 = 3.14 × 100 = 314 (M2) a: the floor area of biogas digester is 314 m2. (2) 314 × 4 = 1256 (M3) a: a total of 1256 m3 of soil needs to be excavated. (3) (3.14 × 20 × 4 + 314) × 0.5 = (251.2 + 314) × 0.5 = 565.2 × 0.5 = 28

How many cubic meters of water is there in a pool with a water depth of 2 meters?

1 mu = 666.7 square meters
666.7x2 = 1333.4m3

A cuboid storage tank, 8.4 meters long, 4.5 meters wide, 2 meters high. What is the floor area of the tank? How many cubic meters can it store water at most

Floor area: 8.4x4.5 = 37.8 square meters
Volume: 8.4x4.5x2 = 75.6m3