Less than 4 / 5 of a number, 7 / 8 is 1 / 48 of 6. Find the number

Less than 4 / 5 of a number, 7 / 8 is 1 / 48 of 6. Find the number

Let this number be X
4x/5-7/8=6×1/48
4x/5-7/8=1/8
4x/5=1
x=5/4
Hope to help you!

How to solve the equation 4.2 + 8.7 + x = 15

4.2 + 8.7 + x = 15 12.9 + x = 15 first calculate the sum of 4.2 and 8.7, x = 15-12.9, and then move to the right, the original + 12.9 "change sign" becomes - 12.9 x = 2.1, get x = 2.1, the landlord adopts me!

5.2-x = 1.7 21 / x = 8.4 solve these equations

5.2-x+x=1.7+x
5.2=1.7+x
1.7+x-1.7=5.2-1.7
x=3.5
(21/x)*x=8.4x
21=8.4x
8.4x/8.4=21/8.4
x=2.5

How to simplify the formula (7 / 12 + 3 / 8-23 / 24) * 24?

(7/12+3/8-23/24)*24
=7/12*24+3/8*24-13/24*24
=14+9-23
=0

In the study of "the relationship between current and resistance under a certain voltage", the circuit is shown in the figure. The constant supply voltage is 3V, and the sliding resistance changes
When studying "the relationship between current and resistance under a certain voltage", the circuit diagram is as shown in the figure. The power supply voltage is constant 3V. The sliding rheostat is marked with "20 Ω 1.5A". Connect the fixed resistance with different resistance values between a and B, close the switch, move the slide P, make the voltmeter indication 3V, and read out the ammeter indication. When the resistance of 20 Ω is connected between a and B, 5 v. the reason may be ()
A. The control voltage of 1.5V is too high
B. The maximum resistance of sliding rheostat is too large
C. The resistance of 20 Ω is too high
D. The power supply voltage 3V is too low
I need to dissect every option,
I'm sorry, I have the wrong choice
A. The maximum resistance of sliding rheostat is too small
B. The power supply voltage 3V is too high
C. The resistance of 20 Ω is too small
D. The control voltage of 1.5V is too high

Because R is connected in series with the sliding rheostat, the sum of the voltages of the two resistors is 3V. When the resistance of the sliding rheostat is 0, the voltage of R is 3V; when all the resistors of the sliding rheostat are connected, the voltage of R is 1.5V, that is, the minimum voltage of R is 1.5V, so AB is wrong, 3V is

If n is any positive integer, then the value of 1 / 2n (n + 1) - 1 is a prime number, how many are n
One half is one in two

The formula you want to say is n (n + 1) / 2-1,
n(n+1)/2-1=（n^2+n-2)/2=（n+2)(n-1)/2
When n = 1, the formula is 0, not prime;
2, when n = 2, the formula is 2, which is a prime number;
3, when n = 3, the formula is 5, which is a prime number;
4, when n > 3, N + 2 and N-1 must be an even number and an odd number, and both are greater than 2, then
(1) When n + 2 is an even number, (n + 2) / 2 is an integer and greater than 1, then (n + 2) / 2 · (n-1) is a composite number, because it has two factors greater than 1: (n + 2) / 2 and (n-1);
(2) When n-1 is even, it is discussed as above;
(these two situations are actually one. I write them separately to make them more clear.)
To sum up, there are two qualified n

The resistance value of a resistance wire is 97 ohm. What is the current passing through it when it is connected to 220 V

I=U/R=220V/97=2.27A

If the chord a B is a parabola y 2 = 8 x through Q (4,1), and Q is the midpoint of the chord, the equation of the straight line a B is obtained

Let a (x1, Y1), B (X2, Y2) then Y12 = 8x1y22 = 8x2 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; subtract the two formulas to get (Y1 + Y2) (y1-y2) = 8 (x1-x2), so 〈 Y1 − y2x1 − x2 = 8y1 + Y2, and & nbsp; & nbsp; Y1 + Y22 = 1 〉 KAB = 4 linear AB equation: Y-1 = 4

The resistance of a section of wire is 2 ohm at 0 degree, and the resistance increases by 0.05 ohm with every 10 degree increase of temperature
Find out the functional relationship between resistance R and temperature T

R=2+0.05*T/10

The equation is solved by proper method X & # 178; + (√ 3 + 1) x + √ 3 = 0

1 1
×
1 √3
(x+1)(x+√3)=0
x=-1,x=-√3