The answer is 7 . you need to add up all the numbers & divide it by the numbers you have
2x+3y=60 solve for x...
x=(60-3y)/2
p=xy^3, using x from above:
p=y^3(60-3y)/2
p=(60y^3-3y^4)/2
dp/dy=(180y^2-12y^3)/2
dp/dy=90y^2-6y^2
dp/dy=0 when:
90y^2-6y^3=0
6y^2(15-y)=0, we know y>0 so
y=15, since x=(60-3y)/2
x=7.5
(We solved it this way because otherwise you get quartic equations and cubic derivatives, yuck :P)
2.5 * 3.5 = 8.75 or 8 3/4 inches long
Answer:
We know that the rectangular plate has measures of:
length = 7.6 ± 0.05 cm
width = 3.1 ± 0.05 cm
(the error is 0.05cm because we know that both measures are correct to one decimal place)
First, the upper bound of the length is equal to the measure of the length plus the error, this is:
L = 7.6 cm + 0.05 cm = 7.65 cm
The upper bound of the area is the area calculated when we use the upper bound of the length and the upper bound of the widht.
Remember that the area for a rectangle of length L and width W, is:
A = W*L
Then the upper bound of the area is:
A = (7.6cm + 0.05cm)*(3.1cm + 0.05cm) = 10.8 cm^2
