Here's 1 lb of butter
What is the area of the wrapper around it?
My answer :
4(11,5 * 6,3) = 289,80cm^2
2(6,3 * 6,3) = 79,38cm^2
289,80 + 79,38 = 369,18cm^2
A = 369,18cm^2
Teacher's answer :
A = L * l
A = 17,8 * 25,2
A = 448,56 cm^2
Why am i wrong?
I'm pretty sure i've done everything right, beside the fact i created my own formula instead of using the illogical one A = 2(Lh + lh + Ll)
On
What you calculated was just the area of the wrapper on just one side of the pound of butter. To find the area of the whole wrapper, we need to find the sum of the areas of all the sides or what we call the surface area.
Since a pound of butter is typically in the shape of a rectangular prism, we can use the following formula to find the surface area:
$SA=2LW+2LH+2WH$
$L=11.5$ cm
$W=6.3$ cm
$H=6.3$ cm
In the end, we should get that the wrapper around a pound of butter has an area of 370.38 cm^2.
Indeed, you're approach successfully calculates the surface area of the pound of butter.
If that is/was the objective, you've achieved it.
My hunch is that in order to construct a wrapper for the pound of butter, you need to find the area of a rectangular sheet of wrapping paper to accommodate both the surface area of the butter, and enough to fold it over the smaller opposing ends.