My brother has 55 science and technology books and some storybooks. The number of science and technology books is 14 times less than that of storybooks. How many storybooks does my brother have?

Suppose brother has x storybooks, 3x-14 = 55, & nbsp; & nbsp; 3x = 69, & nbsp; & nbsp; X = 23, answer: brother has 23 storybooks

The school bought a batch of books, of which 400 are more science and technology books than story books. The number of science and technology books is three times that of story books. How many are there? (solved by equation)

Solution: suppose x story books, 3x science and technology books, & nbsp; & nbsp; 3x-x - = 400, (3-1) x = 400, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 2x = 400, & nbsp; & nbsp; & nbsp; 2x △ 2 = 400 △ 2, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 200, science and technology books: 200 × 3 = 600

1+1+2+3+4+.+98+99+100=?

1+1+2+3+4...+98+99+100
=(1+100)+(2+98)+...50+1
=101+101+...+101+1
=101×50+1
=5051
The following is wrong

The calorific value of physical natural gas in 9 years is 7500000j / m3. If a family uses 10 m3 of natural gas in one month, the heat released by natural gas is

Calorific value refers to the heat released by the complete combustion of a certain fuel, that is to say, the heat released by burning 1 cubic meter of natural gas is 7500000j, then 10 cubic meters of natural gas is of course 7500000j, but the precondition should be marked with complete combustion

Solving equation (1 + 40%) * 80% - unknown = 15

(1 + 40%) * 80% - unknown = 15
Unknowns = (1 + 40%) * 80% - 15
Unknown = (1 + 0.4) * 0.8 * - 15
=1.4*0.8-15
=1.12-15
=-13.88.
Do you have a problem with the equation?

From the point of view of energy conversion, this paper explains why TV sets work at the same time with high sound consumption more than low sound consumption
Such as the title

The larger the mechanical energy is, the greater the power consumption is

2A & # 178; - 7ab + 6B & # 178; factorization,

1 -2
×
2 -3
The AB coefficient is - 4-3 = - 7
accord with
So the original formula = (a-2b) (2a-3b)

How much is 150 grams

500 grams is 1 jin, then 150 grams is 0.3 Jin

2 & # 185; = 2 2 & # 178; = 4 2 & # 179; = 8 2. Through observation, write 2 & # 178; - # 185; the last number is
2 & # 185; = 2 & # 178; = 4 2 & # 179; = 8... Through observation, write 2 & # 178; - # 185; the last number is

2 4 8 6 cycles every four cycles
21 is 2
The number is 2097152
Using Excel is a very simple step

1. An electric furnace marked with "220V 1000W" is connected to the 220V power supply and works for 0.5h to consume electric energy___ KW. H, the heat generated is_ J.
2. There is a kind of household electric rice cooker. There are two resistors R1 and R2 in parallel in the circuit, which are controlled by S1 and S2 respectively. When S1 and S2 are closed, the two heating elements R1 and R2 heat the cooker at the same time, and the cooker is in the high temperature heating state; when only S1 is closed, the cooker is in the low temperature insulation state. It is known that the voltage of household circuit is 220 V, and the resistance value of constant resistance R2 is 88 Ω, The heating power of electric rice cooker at low temperature is 40W
(1) What is the current through resistance R2 in high temperature heating state?
(2) What is the resistance value of resistance R1 at low temperature?
(3) When heating at high temperature, what is the heating power of the electric cooker?
3. There are two resistors R1 and R2. If only R1 is connected to the power supply, the heat generated in one minute is 160J. If only R2 is connected to the power supply, the heat generated in one minute is 40J. If R1 and R2 are connected in series to the same power supply, the total heat generated by the current in one minute is 160J J. If R1 and R2 are connected in parallel with the power supply, the total heat generated by the current in one minute is 0___ J.
4. If a resistor passes 2A current, the heat generated in a certain time is Q. if the current increases to 4a, the heat generated in the same time is ()
A.Q/2 B.Q/4 C.4Q D.2Q
5. Resistor R1 and R2 are connected in series in the circuit with voltage of u, and R1 > R2, the heat generated in time t is Q1 and Q2 respectively. If these two resistors are connected in parallel, and then connected into the circuit with voltage of U / 2, the heat generated in time t is Q1 'and Q2', respectively, the relationship of heat is ()
A.Q1Q1',Q2

1. W = Pt = 1kW * 0.5h = 0.5kwhq = Pt = 1000W * 1800s = 1.8 * 10 ^ 6j2, I2 = u / r2 = 220V / 88 Ω = 2.5ar1 = u ^ 2 / P1 = (220V) ^ 2 / 40W = 1210 Ω P total = P1 + P2 = u ^ 2 / R1 + ui2 = (220V) ^ 2 / 1210 Ω + 220V * 2.5A = 40W + 550W = 590w3

My brother has 55 science and technology books and some storybooks. The number of science and technology books is 14 times less than that of storybooks. How many storybooks does my brother have?