Math CentralQuandaries & Queries


Subject: algebra
Name: jadesola
Who are you: Student

p=2l+2w find l

We have two replies for you.


What you need is to manipulate the equation, always maintaining the equality and end with an expression of the form

l = some expression that doesn't contain l

You want l on the left of the equation so I would first rewrite it

2l + 2w = p

You don't want the 2w term on the left of the equality so add -2w to each side. This maintains the equality and gives


2l + 2w -2w = p -2w so
2l = p - 2w

You are almost there, you have 2l on the left rather than l so divide both sides by 2 to get

2l/2 = (p - 2w)/2 and hence
l = (p -2w)/2

Now for practice find l if p = 3l - 2w and let me know what you got for l.



Hi there.

With any equation like this, you just have to make sure that what you
do to one side of the equation you do as well to the other. Then go
step by step unpeeling the variable you want to find (in your case
this is l). You kind of use a backwards-bedmas to do this:

p = 2l + 2w

first remove the added term 2w by subtracting 2w from both sides:

p - 2w = 2l + 2w - 2w
p - 2w = 2l

now remove the 2 from the 2l by dividing both sides by 2:

( p - 2w ) / 2 = 2l / 2
p / 2 - w = l

So l is p / 2 - w. That's how you solve one of these equations for
any particular variable you want.

Hope this helps,
Stephen La Rocque.

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