# Help with formulas?

• Sep 30th 2009, 06:59 PM
ranfan2
Help with formulas?
Would someone please explain to me how to solve these? I'm completely lost and can't even figure out one of the problems on my homework. I would greatly appreciate step-by-step instructions that are as non-confusing as possible. (Worried)

A=115+1/2(p+s) solve for s=?

P=2w+2l solve for w=?

Also, this word problem:
Set up an equation for the given application problem.
The perimeter of standard - size copier papper is 99 cm. The width is 6.3 cm less than the length. Find the length and the width.

If you would like to just do one that's fine, I'm just in desperate need of some instructions.
• Sep 30th 2009, 07:05 PM
elninio
Your first question is strange. I suppose its not looking for a concrete answer. in the first case, just isolate s to one side.
A-115-1/2p=1/2s
2A-230-p=s

Try this for the second one.

The perimeter of standard - size copier papper is 99 cm. The width is 6.3 cm less than the length. Find the length and the width.
Let x be length and y be width.

Perimeter = x+y+x+y = 2x+2y
99=2x+2y

y=x-6.3

Substituting, we get...

99=2x+2(x-6.3)
99=4x-12.6
111.6=4x
x=27.9cm
We know y is 6.3 less than this so,
y=21.6cm
• Sep 30th 2009, 07:12 PM
ramiee2010
Sol. 1)
$\ a= 115 + \frac{1}{2} (p+s)$
$\ a-15 = \frac{1}{2} (p+s) \$ or $\ \frac{1}{2} (p+s) =\ a-15$
$p+s =2(a-15)$
$s =2(a-15) -p$
• Sep 30th 2009, 07:15 PM
ramiee2010
sol. 2)
$P=2w+2l$
$P-2l=2w$
$2w=P-2l$
$w=\frac{1}{2}(P-2l)$
• Sep 30th 2009, 07:27 PM
elninio
Ramiee, In sol 1, 15 should be replaced by 115.
• Sep 30th 2009, 07:46 PM
ramiee2010
oops
• Sep 30th 2009, 08:12 PM
Wilmer
A = 115 + 1/2(p + s)

Don't wait; get rid of fraction RIGHT AWAY; multiply by 2:
2A = 230 + p + s

s = 2A - 230 - p

Easier, right?