Can you explain this ?

[bbeam01]

[attachment=0:26t9ao83]math.jpg[/attachment:26t9ao83]

Need help explaining this . Please help !

 

[Denis]

C'mon...substitute 5 for w and get the perimeters...did you at least TRY?

 

[bbeam01]

I can do that part. Look at the second part of the problem, " Is there a value for w that would make the perimeters equal ? Explain". This is the part I need explained.

 

[bbeam01]

I can solve for the perimeters of both rectangles but my problem is that this comes from my fourth-graders homework and I don't think they're actually trying to solve for the value of "w" but want the theory behind why they could or couldn't be equal. Could you please explain this ?

 

[mathgeek]

I believe I have the solution to you problem. Set the perimeters equal to each other. When you solve for w, plug it back in and you will see that they are equal.

Have Fun

Also, if you need me to show you the work, just tell me.

 

[bbeam01]

Thank You mathgeek for the reply. If you would, please show me the work and could you please explain as well ?

 

[mathgeek]

OK, first of all,

2(2w+4)+2(w)=2(w+3)+2(3w-5) > I doubled each part of the equation to account for the opposite side of the rectangle. I also set them equal because the question asked what value of w would make it equal.

4w+8+2w=2w+6+6w-10 > I just distributed in this step

6w+8=8w-4 > Here I simplified the equation

12=2w > more simplifying

w=6

Checking the answer to see that the perimeters are equal

2(6) +2[2(6)+4]=

12+2[12+4]

12+2[16]

12+32

44


2(6+3)+2[3(6)-5]

2(9)+2[18-5]

18+2(13)

18+26

44

I hope that helps you with your problem.

 

[bbeam01]

Yes - That made it very clear. Thank You for the help and for your quick answers to my questions. You saved the day !

 

[chrisr]

You could also say w+(2w+4) equals (w+3)+(3w-5) if the perimeters are to be equal,
since the other sides are the same as those
2z = 2k means z = k

So 3w+4 = 4w-2
so 3w-3w+4=4w-3w-2 so 4=w-2 so w is 6