We know that
[surface area ]=2*[area of the base]+[perimeter of the base]*height
area of the base=10*8.7/2-----> 43.5 cm²
perimeter of the base=10*3----> 30 cm
height of the prism=15 cm
[surface area ]=2*[43.5]+[30]*15------->537 cm²
the answer is
<span>the approximate surface area of the prism is 537 cm</span>²
I cannot see Zoe's work to explain the error, but the correct method of solving is listed:
x is the number of 30-second ads
y is the number of 60-second ads
x+y=12(60)=720 would be the first equation; this is because while the ads together make 12 minutes, the ad times are in seconds. This means we must multiply 12 by 60.
y=2x is the second equation
Our system is then
x+y=720
y=2x
We will use substitution to solve this. Plug 2x in place of y in the first equation:
x+2x = 720
Combine like terms:
3x = 720
Divide both sides by 3:
3x/3 = 720/3
x = 240
Substitute this value in for x in the second equation:
y=2(240)
y=480
To factor completely 18b - 32, we factor out the common factor of the two terms and divide each of term by the common factor.
18b - 32 = 2(18b/2 - 32/2) = 2(9b - 16)
