Help me with this math problem?(easy-7th grade level)?

Question

1.)the perimeter of a rectangle is 60 feet.The length is twice the width.What are the the dimensions of the rectangle ?

2.)Allen had a rope that was 12 3/4 feet long.He wanted to make a swing with the rope,and he used 7 1/2 feet to make the swing .How many feet of rope did he have left?express your answer as a decimal.

3.)In 1990,the U.S. debt was 3.0 x 10 to the 12th power dollars.Write this number out in standard form.

Answer 1

1.) If the length is twice the width, consider this:

If the perimeter is 60 feet, and the length is twice the width, then two width's is one length which then there are three length's. If you put the two width's together it makes one length, right? so then u got 3 length's. Divide total perimeter 60, by 3 lengths. which is 20 feet. So you take your two length's 20 and 20, the other length is 20 divide that into two that makes 10 feet and 10 feet for the width's.  

Width of side A: 10 feet

width of side B: 10 feet

length of side A: 20 feet

length of side B: 20 feet

which equals 20+20+10+10= 60 feet

does that answer your question, and help you out?

Answer 2

1. 10X20 (10+10+20+20)

(2X+4X=60 --> there are 4 sides, 2X=shorter side, 4X=double, long side, 60=6x, therefore x=10, and the side are 2x each, so they are 20.)

2. 3/4=.75 and 1/2=.5, therefore 12.75-7.50= 5.25 feet

3. 10^12= the number of zeros, therefore 3000000000000. 12 zeros= trillion, so 3 trillion dollars.

Hope that helped!

Answer 3

1.  length = 2w

     2(2w) + 2w= 60

     6w=60

      w=10,

10ft x 20ft rectangle. Which is read, 10 feet by 20 feet

2. 12.75-7.50= 5.25 ft of rope left

3. 30 to the 12th power, use a calculator  

Answer 4

P=2(l+w) P=2l+2w  length is 20 width is 10

12 3/4- 7 1/2= 12 3/4-7 2/4= 5 1/4

3 x 10^12=3,000,000,000,000

Answer 5

1.) Length=20ft Width=10ft

2.) 5 1/4ft or 5.25 feet

3.) 3,000,000,000,000

Answer 6

L = length

W = width

2L + 2W = 60

L = 2W

Substitute:

2L + (L) = 60

3L = 60

L = 20

Now put that back into either of the original equations:

(20) = 2W

W = 10

I think you can do the other two.