Thread: please help

how do you solve this
if av=63 vb=6.0 fb=45
what are the steps you use

Originally Posted by boondock

how do you solve this http://www.caraudio911.com/tutorials...images/001.gif
if av=63 vb=6.0 fb=45
what are the steps you use

PEMDAS my friend. Start with the squared term in the denominator, evaluate the rest of the fraction. Then remember to multiply then add.

Jameson

so 0.159 squared is .025 right? then i divide by 45? i get 5.62^-3 i think i did somethig wrong or is it 177.866

Start by evaluating the (Fb/0.159)^2 term.
This is:

(45/0.159)^2 ~= (283.02 )^2 ~= 80.1 10^3.

RonL

how do you solve this
Lv = {[Av *1.84 *10^8] / [Vb *1728 *(Fb/0.159)^2]} -{0.823*sqrt(Av)}
if av=63 vb=6.0 fb=45
what are the steps you use

Lv = {[Av *1.84 *10^8] / [Vb *1728 *(Fb/0.159)^2]} -{0.823*sqrt(Av)}
Lv = {[63 *1.84 *10^8] / [6.0 *1728 *(45/0.159)^2]} -{0.823*sqrt(63)}
Lv = {[115.92 *10^8] / [10,368*(283.019)^2]} -{0.823 *7.937}
Lv = {[115.92 *10^8] / [10,368*80,100]} -{6.532}
Lv = {[115.92 *10^8] / [830,476,800]} -{6.532}
Lv = {[115.92 *10^8] / [8.305 *10^8]} -{6.532}
Lv = {(115.92 / 8.305) *10^(8-8)} -6.532
Lv = {13.958 *10^(0)} -6.532
Lv = {13.958 *1} -6.532
Lv = 13.958 -6.532
Lv = 7.426 -----------------answer.

thank you so much i see now

how did you get Lv = {[115.92 *10^8] / [8.305 *10^8]} -{6.532}

where did this come from [8.305 *10^8]

how did you get Lv = {[115.92 *10^8] / [8.305 *10^8]} -{6.532}

where did this come from [8.305 *10^8]

I guess these are for me to answer.

--------------------------

how did you get Lv = {[115.92 *10^8] / [8.305 *10^8]} -{6.532}

Okay, here is a copy of my solution:

Lv = {[Av *1.84 *10^8] / [Vb *1728 *(Fb/0.159)^2]} -{0.823*sqrt(Av)}
Lv = {[63 *1.84 *10^8] / [6.0 *1728 *(45/0.159)^2]} -{0.823*sqrt(63)}
Lv = {[115.92 *10^8] / [10,368*(283.019)^2]} -{0.823 *7.937}
Lv = {[115.92 *10^8] / [10,368*80,100]} -{6.532}
Lv = {[115.92 *10^8] / [830,476,800]} -{6.532}
Lv = {[115.92 *10^8] / [8.305 *10^8]} -{6.532}
Lv = {(115.92 / 8.305) *10^(8-8)} -6.532
Lv = {13.958 *10^(0)} -6.532
Lv = {13.958 *1} -6.532
Lv = 13.958 -6.532
Lv = 7.426 -----------------answer.

There are 11 lines. The eleventh is the answer.
You are asking me how I got the 6th line.
If I say I got it by doing the first 5 lines above it, would you believe me?

-----------------------

where did this come from [8.305 *10^8]

Let us go back to the 5th line,
Lv = {[115.92 *10^8] / [830,476,800]} -{6.532}

There is the 830,476,800.
It is 830Millions, +476Thousands, +800.
The decimal point is at the end of the 800, or at the end of the 830,476,800.
If you want to express the 830,476,800 in engineering mode, or in a small number times 10^(something), then you place the decimal point all the way to the left, after the first significant number, after the the 8 of the 830Millions.
In so doing, how many decimal places, or how many numbers did you pass over? Count them. From the decimal point being at the end of 830,476,800 to the decimal point being moved to between 8 and 3 of the 830Millions?
Did you count 8 decimal places? If yes, then you are correct.

So, now the 830,476,800. is transformed into
8.30476800 *10^8
or, 8.304768 *10^8

Since in your original equation you used only 3 decimal places for the numbers less than 1, [1.84, 0.159, 0.823], then I followed your lead. I reduced/expressed the 8.304768 to 8.305 only.
Do I have to ask you why I used "5" only for the whole "4768"?
You have not been taught in school about "rounding up" yet?

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May I add this:

830,476,800
is the same as 8.305 *10^8,
the same as 83.048 *10^7,
the same as 8,304.768 *10^5,
the same as 0.00083 *10^12

ok i got you thanks for all the help you are the best

ok i got you thanks for all the help you are the best

i did an other one can you tell me if it is ok
16*1.84*10^8/1.296*1728*80100-3.292 =13.118

av=16 vb=1.296 fb=45

i did an other one can you tell me if it is ok
16*1.84*10^8/1.296*1728*80100-3.292 =13.118

av=16 vb=1.296 fb=45

Yes. Very good.

thanks