more help me with Ohm resistor !!!!!!!?

Question

A 39k Ohm resistor is connected in parallel with a 62k Ohm resistor and a 43 k Ohm resistor. How much resistance should be connected in parallel with these three resistors to produce an equivalent resistance of 7k Ohm

Answer 1

resistance is futile.

Answer 2

ok here you are :
"the reciprocal of the total resistance (equivalent resistance) of the circuit is equal to the sum of the reciprocals of the resistances of the resistors"... so
1/R = 1/R1 + 1/R2 + 1/R3 + 1/R4
and we want to know (R4)
so ...
1/7= 1/39+1/62+1/43+1/R4
R4 = about 12.8 ohms

Answer 3

First we have to get the Rt, which is,
Rt =

R1R2R3
_______________________

R1R2 + R2R3 + R3R1

which is, Rt =15.4KΩ, according to the given resistors.
Then, we need 7KΩ, so we substitute and we get, the
final result, Rx.

1/7KΩ = 1/Rt + 1/Rx

1/Rx = 1/7KΩ - 1/15.4KΩ

Rx = 1/7.79X10^ -5 KΩ

Rx = 12.8 KΩ is the resistor that you need.

Answer 4

Got a scientific calculator? Enter
39000[1/x]+62000[1/x]
+43000[1/x]-7000[1/x]=[1/x]

[1/x] is the reciprocal key and may be identified[x-1]