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1/R=1/6.25 + 1/7.5Anybody here good with math and formulas? I have a problem I can't get past.

What is the total resistance of this circuit?

1/R = 1/6.25 + 1/7.5

Also, can you list step by step on how you figured this out?

Thanks a ton :thumbup:

1/R= .16 + .133 = .293

1/R= .293

Multiply both side by R

1= .293 x R

divide both sides by .293

1/.293 = R

3.41= R

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742 Posts

You are using a calculator, right?

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2,969 Posts

If those two resistors are in parrallelAnybody here good with math and formulas? I have a problem I can't get past.

What is the total resistance of this circuit?

1/R = 1/6.25 + 1/7.5

Also, can you list step by step on how you figured this out?

Thanks a ton :thumbup:

I.E. 6.25 & 7.5

then its 3.44 ohms.

1/6.25 = .16

1/7.5 = .13

.16 + .13 = .29

1/.29 = 3.44

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7,455 Posts

This is for a parallel circuit, A good little "check sum" is that your solution will be less than any of your individual resistances. If you come up with a number larger than any of your original resistance values you have done something wrong.Anybody here good with math and formulas? I have a problem I can't get past.

What is the total resistance of this circuit?

1/R = 1/6.25 + 1/7.5

Also, can you list step by step on how you figured this out?

Thanks a ton :thumbup:

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7,455 Posts

Dennis doesn't use a calculator, Dennis is a calculator!You are using a calculator, right?

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13,543 Posts

get rid of denominators.

What is the total resistance of this circuit?

1/R = 1/6.25 + 1/7.5

Also, can you list step by step on how you figured this out?

Thanks a ton :thumbup:

6.25*1/R = 6.25*1/6.25+ 6.25*1/7.5

6.25/R= 1 + 6.25/7.5

7.5*6.25/R = 7.5 + 7.5*6.25/7.5

7.5*6.25/R = 7.5 + 6.25

7.5*6.25*R/R = (7.5+6.25)*R

7.5*6.25 = 13.75R

7.5*6.25/13.75 = R

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742 Posts

I meant that for the OP. He has the right formula, was just wondering if he didn't know how to punch it in correctly.five.five-six said:Dennis doesn't use a calculator, Dennis is a calculator!

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4 Posts

Thanks guys awesome work. 3.41 is correct.

Sent from my DROID RAZR using Tapatalk

Sent from my DROID RAZR using Tapatalk

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3,838 Posts

That sure looks like a lot of key strokes to get the answer when all you have to do is add the reciprocals of all of the resistors that are in parallel and then take the reciprocal of the sum.get rid of denominators.

6.25*1/R = 6.25*1/6.25+ 6.25*1/7.5

6.25/R= 1 + 6.25/7.5

7.5*6.25/R = 7.5 + 7.5*6.25/7.5

7.5*6.25/R = 7.5 + 6.25

7.5*6.25*R/R = (7.5+6.25)*R

7.5*6.25 = 13.75R

7.5*6.25/13.75 = R

http://www.sengpielaudio.com/calculator-paralresist.htm

Parralel is just X^-1 + X^-1 on a calculator.

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2,508 Posts

common coreget rid of denominators.

6.25*1/R = 6.25*1/6.25+ 6.25*1/7.5

6.25/R= 1 + 6.25/7.5

7.5*6.25/R = 7.5 + 7.5*6.25/7.5

7.5*6.25/R = 7.5 + 6.25

7.5*6.25*R/R = (7.5+6.25)*R

7.5*6.25 = 13.75R

7.5*6.25/13.75 = R

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3,838 Posts

That works too, but still more keystrokes than using the reciprocal key. 3 key strokes to raise X to the -1 power and only one using the reciprocal key to get the same result.Parralel is just X^-1 + X^-1 on a calculator.

Thats the only way I know from being taught at night school.That works too, but still more keystrokes than using the reciprocal key. 3 key strokes to raise X to the -1 power and only one using the reciprocal key to get the same result.

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3,838 Posts

Most calculators that have a X^y key also have the reciprocal (1/x) key.Thats the only way I know from being taught at night school.

For the problem in this thread, enter 6.25, then hit 1/x, then hit +, then enter 7.5, then hit 1/x, then hit =, then hit 1/x and you have your answer.

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