# How I can find U2 here

1. Jul 1, 2012

### manal950

http://store2.up-00.com/June12/Pdb64021.jpg [Broken]

I will try

391.4368 + 24.264U2 + 2.2332 / 0.8 = 30.5764/1
24.461 = 391.436+24.2564U2 + 12.232

24.461 - 391.436 - 12.232 = 24.2564U2
U2 = (24.461 - 391.436 - 12.232 ) / 24.2564
U2 = 15.6

Last edited by a moderator: May 6, 2017
2. Jul 1, 2012

### Staff: Mentor

Don't ignore parentheses.

You already made a mistake in your first step. Where did you got 2.2332 from?

3. Jul 1, 2012

### manal950

391.4368 + 24.264U2 / 0.8 + (15.290U2) = 30.5764

Now what will I do

and this next ..

391.4368 + 24.264U2 + 2.2332 / 0.8 = 30.5764/1

4. Jul 1, 2012

### Staff: Mentor

Don't ignore parentheses. 391.4368 + 24.264U2 / 0.8 and (391.4368 + 24.264U2) / 0.8 are two different things.

Apart from lack of parentheses your first step looks OK now. But I still don't know where did you got 2.2332 from.

$$\frac{a+b}c = \frac a c + \frac b c$$

5. Jul 1, 2012

### manal950

391.4368 + 24.264U2 / 0.8 + (15.290U2) = 30.5764

391.4368 + 24.264U2 + (15.290U2) /0.8= 30.5764

now Is this step is correct ?

Last edited: Jul 1, 2012
6. Jul 1, 2012

### Staff: Mentor

No, it is wrong. You can't move expressions at random, there are strict rules that you need to follow.

You are still ignoring parentheses, you are wasting your time and my time.

7. Jul 1, 2012

### vela

Staff Emeritus
I think the 2.2332 is supposed to be 12.232, which is what you get by multiplying 15.290 by 0.8.

8. Jul 1, 2012

### manal950

So now is my answer is correct or not ... ??

9. Jul 1, 2012

### vela

Staff Emeritus
It's kind of hard to follow what you did, so I'd have to say "probably not." First, take the sage Borek's advice and use parentheses. As he noted, a+b/c means something completely different from (a+b)/c. Don't make others guess what you mean when you can write it in a way that's perfectly clear.

So you're starting off with

30.581((12.8+0.8u2)/0.8) + 15.290u2 = 30.5764.

Now show us one step at a time what you're doing. It might help if you explained in words that you're doing each step as well.

10. Jul 1, 2012

### manal950

30.581((12.8+0.8u2)/0.8) + 15.290u2 = 30.5764.

Now I will multiply 30.581 X ((12.8+0.8u2) / 0.8

= 91.4368 + 24.4648U2 /0.8 + 15.290u2 = 30.5764.

now I will bring 91.4368 other side
24.4648U2 /0.8 + 15.290u2 = 30.5764 - 91.4368
24.4648U2 /0.8 + 15.290u2 = -60.8604
now I will apply this rule a+b/c to left side
24.4648U2 + 15.290u2 /0.8 = -60.8604
Now
-60.8604 (0.8) = 24.4648U2 + 15.290u2
u2 = -9.6

Note : U2 the 2 is not square

11. Jul 1, 2012

### vela

Staff Emeritus
How did you get
$$91.4368 + \frac{24.4648u_2}{0.8} + 15.290u_2 = 30.5764?$$

12. Jul 2, 2012

### Staff: Mentor

I think I know what is going on. You don't ignore parentheses - you have no idea they are necessary. You are consistently making the same error, which suggests you think (1+2)/3=1+2/3. That's incorrect. (1+2)/3=1/3+2/3. Each expression from the sum in the numerator must be divided separately.