I have a few math questions please...?

Question

#1.)

Ok. The first one shows an open box with an aerial view. It shows 1 ft as the length of all sides and 6 in. the height. There is no cover. I am asked to find the surface area.

This is what I have, but I am not sure:

Front = 12" x 6" = 72"
Back = (same) 72"
Side= (same) 72"
Side = (same) 72"
Bottom = 12" x 12" = 144"
Sum = 432 in.^2, or 36 ft^2



#2) The next one is a bit more difficult to describe.

There is a shape that looks something like this:



___________
)__________| Height 2 cm
<----3 cm------>

It says that the bottom piece is 3 cm, the height is 2 cm, and then there is a cutout of a half circle there on the left. The base on the right side is a right angle of 90 degrees. I need to find the perimeter.

This is what I have so far:

P = 2(l+w)
P=2(3cm + 17 cm)
P=6cm + 150 cm
P=156 cm

Thanks so much in advance for your help!

Answer 1

q1. 2(4*1*0.5+1*1)=6ft2

q2. A=3+3+2+pi=(8+pi) in

Answer 2

#1
The surface area calculation look OK, but 432 square inches is only 3 square feet. (divide by 12 twice)

#2
I'm not sure where 17 cm comes from, or how you got 150 cm, for that matter. The straight sides are 3+2+3 = 8 cm, and the half circle is (2*pi*r)/2 = pi*1. So the answer is (8+pi) cm.

Answer 3

432 in^2 is correct but it is 432/144 = 3 ft^2

The perimeter is 3+3+2 +pi = 8+pi cm = 11.14 cm

Where in the world did your 17 cm come from? The length of the semicircle is pi*r = pi*1 = pi.

Answer 4

#1 If the box is open, you count inside & outside surfaces?
That would double your answer: 2(4(12 x 6) + (12 x 12)) = 864

#2 Where did the 17cm in line 2 come from?
How did it get to 150 cm in line 3?
You made no attempt to count the semi-circle.