I ran 10 times the perimeter of a field at the rate of 12 km per hr for 30 mins. if field length is twice it's width. what is the area in square meters?

Question

Homework 7th grade

Answer 1

12 km/hr for 30 mins

 

30 mins = 1/2 hour

 

(12 km/hr)(1/2 hr) = 6 km = 6000m

 

10 times around the field totaled to 6000m

The perimeter of the field is 6000/10 = 600m

 

L = 2W since the length is twice the width of the field

 

P = 2L + 2W

600 = 2(2W) + 2W

600 = 4W + 2W

600 = 6W

W = 100m

 

The width of the field is 100m

The length is 2W = 200m

 

The area of the field in square meters is 100*200 = 20,000m²

Answer 2

If the width of the field is represented by w, then the length is 2w (since it is twice the width). The perimeter is the sum of two of each, giving

 

P = 2w + 2(2w) = 2w + 4w = 6w.

 

You ran 10 times this perimeter, which is 10·6w = 60w.

 

Running at 12 km/hr for 1/2 hour, you ran 6 km.

 

So, we now know that 60w = 6 km, or that the width of the field is 6/60 = 1/10 km. The length is twice that, or 2/10 = 1/5 km, so the area of the field is

 

1/10 · 1/5 = 1/50 sq km.