How to add, subtract, multiply and divide these four numbers into 24

How to add, subtract, multiply and divide these four numbers into 24

Hello:
(4-4÷7）×7＝24

Use 8 8 3 3 to calculate 24. You can use addition, subtraction, multiplication, division and brackets
Ah... The number is 8, 3, 3. It can't be reversed.
The order of 3 7 numbers can not be reversed

8/(3-8/3)

How to calculate equal to 24 by adding, subtracting, multiplying and dividing brackets

5*(5-1/5)=24

The name plate "3000r / kWh" is connected with an electric appliance. Within 5min, the number of turns of the electric energy meter turntable is 45
There is a watt hour meter marked with the name plate "3000r / kWh", and an electric appliance is connected to the circuit. Within 5min, the number of revolutions of the rotary table of the watt hour meter is 45?
(2) How much power is consumed by electrical appliances?

In the first question, 45 RPM divided by 3000 R / kWh is equal to 0.015 kwh, in the second question, 0.015 kwh × 3.6 × 10 ^ 6 is equal to 54000 joules, P = w / T = 54000 joules △ (5 × 60) = 180 watts

18(a－b)³－12b(b－a)²

18(a－b)³－12b(b－a)²
=18(a-b)^3-12b(a-b)^2
=6(a-b)^2[3(a-b)-2b]
=6(a-b)^2(3a-5b)

Finding atomic weight
There are three kinds of monobasic bases a, B and C, and the ratio of their chemical formula is 3:5:7. For example, 7 mol a, 5 mol B and 3 mol C are mixed evenly, and the mixed alkali is 5.36 g, which is completely reacted with 50 ml sulfuric acid solution (density 1.1 g / ml) with 13.37% solute. The atomic weights of metal elements in the three kinds of bases are calculated

The results show that n (H2SO4) = 50 × 1.1 × 13.37% / 98 = 0.075mol, n (H +) = 0.15mol, the amount of 5.36g mixed alkali is 0.15mol, which contains 0.07mol a, 0.05mol B, a0.03mol a, B and C. suppose that the amount of a, B and C is 3x 5x 7x0.07 × 3x + 0.05 × 5x + 0.03 × 7x = 5.36g, x = 8, and a, B and C is 3x 5x 7x0.07 × 3x + 0.05 × 5x + 0.03 × 7x = 5.36g, x = 8

1、 The following formula (which can be simplified) is 8 23 1 3 45 - (30 - + 8 -) 2 - - 1 - + 0.75 11 5 11 4 16
2、 Calculation (those that can be simplified must be simplified)
3.6—3.6X0.8
The first question can't be typed in written form. Let me say it in Chinese: 45 and 11 / 8 minus (30 and 5 / 2 plus 8 and 11 / 3) 2 and 4 / 1 minus 1 and 16 / 3 plus 0.75

First question
1. Remove the brackets and turn it into a continuous subtraction question. Then first calculate 8 out of 45 and 11 minus 3 out of 8 and 11 to get 5 out of 37 and 11, then calculate 5 out of 37 and 11 minus 2 out of 30 and 5, and get 3 out of 7 and 55
2. Turn 0.75 into 3 / 4, and then calculate 3 / 4 plus 3 / 4 to get 4, and then subtract 1 / 16 to get 2 / 16 to 13
Second question
3.6 * (1-0.8) = 3.6 * 0.2 = 7.2

When the voltage at both ends of the constant resistance R increases from 3V to 4V, the current in the circuit changes 200mA, and the electric power of the constant resistance changes______ W. The resistance value of the constant resistance is______ Ω．

When the voltage at both ends of the resistance is 3V, the current through the resistance is I1 = u1r = 3VR, and the electric power of the resistance is P1 = u12r = (3V) 2R; when the voltage at both ends of the resistance is 4V, the current through the resistance is I2 = u2r = 4vr, and the electric power of the resistance is P2 = (4V) 2R; ∵ when the voltage at both ends of the fixed value resistance R increases from 3V to 4V

It is proved that φ (n) + σ (n) = 2n if and only if n is prime
From left to right will not It shouldn't be very difficult

Wait for the God who is proficient in analytic number theory!
I'd rather reduce the adoption rate than mark it!

The resistance of a resistance wire is 97 ohm. When it is connected to a voltage of 220 volts, what is the current flowing through it

I=U/R=220/97=2.3A