3. A rectangular classroom is twice as long as it is wide, and its area is 800 square feet. Find the dimensions of the classroom.

Question

3.	A rectangular classroom is twice as long as it is wide, and its area is 800 square feet.  Find the dimensions of the classroom.

anonymous · Answer

800 = 2x(x)
800 = 2x^2
0 = 2x^2 - 800
0 = 2(x^2 - 400)
Can you solve the quadratic now?

anonymous · Answer

whould it be 2(x+2)(x-200)

anonymous · Answer

No. Do you recognize that it's a difference in squares pattern?
$$a^{2} - b^{2} = (a - b)(a + b)$$

anonymous · Answer

alright

anonymous · Answer

now i do

anonymous · Answer

would the answer be 2(x-20)(x+20)
X=20 X=-20

anonymous · Answer

There you go.

anonymous · Answer

Do yuo understand that dimensions can't be negative? Therefore, the width is 20. Then, the length is twice as long as the width, so 2(20) = 40
40 is the length.
20 is the width.

anonymous · Answer

yes thank you, do you think you could help me with a few others

anonymous · Answer

A plane is flying nonstop from Pittsburgh to Los Angles, a distance of about 2400 miles.  After 1 hour 15 minutes in the air, the plane flies over St Louis (a distance of 800 miles from Pittsburgh).  Estimate the time the plane will arrive in Los Angles if it departs from Pittsburgh at 12 p.m.(noon).