surface area (S) of a right rectangular solid is:
S = 2*L*W + 2*L*H + 2*W*H (equation 1)
where:
L = length
W = width
H = height
-----
you have:
L = 7
W = a
H = 4
-----
formula becomes:
S = 2*7*a + 2*7*4 + 2*a*4
simplify:
S = 14*a + 56 + 8*a
combine like terms:
S = 22*a + 56
-----
answer is:
S = 22*a + 56 (equation 2)
-----
to prove, substitute any value for a in equation 2:
let a = 15
S = 22*a + 56 (equation 2)
S = 22*15 + 56
S = 330 + 56
S = 386
-----
since a = 15, then W = 15 because W = a
go back to equation 1 and substitute 15 for W:
S = 2*L*W + 2*L*H + 2*W*H (equation 1)
where:
L = length
W = width
H = height
-----
you have:
L = 7
W = 15
H = 4
-----
equation 1 becomes:
S = 2*7*15 + 2*7*4 + 2*15*4
perform indicated operations:
S = 210 + 56 + 120
S = 386
-----
surface area is the same using both equations so:
equations are good.
formula for surface area of right rectangle in terms of a is:
S = 22*a + 56
-----
<span>3 is to 4 as 12 is to x, or 3/4 = 12/x </span>
I hope this helps you
18c-27d
9×2c-9×3d
9 (2c-3d)
let's firstly convert the mixed fractions to improper fractions.
![\bf \stackrel{mixed}{3\frac{1}{2}}\implies \cfrac{3\cdot 2+1}{2}\implies \stackrel{improper}{\cfrac{7}{2}}~\hfill \stackrel{mixed}{1\frac{1}{3}}\implies \cfrac{1\cdot 3+1}{3}\implies \stackrel{improper}{\cfrac{4}{3}} \\\\[-0.35em] \rule{34em}{0.25pt}](https://tex.z-dn.net/?f=%5Cbf%20%5Cstackrel%7Bmixed%7D%7B3%5Cfrac%7B1%7D%7B2%7D%7D%5Cimplies%20%5Ccfrac%7B3%5Ccdot%202%2B1%7D%7B2%7D%5Cimplies%20%5Cstackrel%7Bimproper%7D%7B%5Ccfrac%7B7%7D%7B2%7D%7D~%5Chfill%20%5Cstackrel%7Bmixed%7D%7B1%5Cfrac%7B1%7D%7B3%7D%7D%5Cimplies%20%5Ccfrac%7B1%5Ccdot%203%2B1%7D%7B3%7D%5Cimplies%20%5Cstackrel%7Bimproper%7D%7B%5Ccfrac%7B4%7D%7B3%7D%7D%20%5C%5C%5C%5C%5B-0.35em%5D%20%5Crule%7B34em%7D%7B0.25pt%7D)
![\bf \begin{array}{ccll} miles&hours\\ \cline{1-2}\\ \frac{7}{2}&1\\[0.8em] m&\frac{4}{3} \end{array}\implies \cfrac{~~\frac{7}{2}~~}{m}=\cfrac{~~1~~}{\frac{4}{3}}\implies \cfrac{7}{2m}=\cfrac{3}{4}\implies 28=6m \\\\\\ \cfrac{28}{6}=m\implies \cfrac{14}{3}=m\implies 4\frac{2}{3}=m](https://tex.z-dn.net/?f=%5Cbf%20%5Cbegin%7Barray%7D%7Bccll%7D%20miles%26hours%5C%5C%20%5Ccline%7B1-2%7D%5C%5C%20%5Cfrac%7B7%7D%7B2%7D%261%5C%5C%5B0.8em%5D%20m%26%5Cfrac%7B4%7D%7B3%7D%20%5Cend%7Barray%7D%5Cimplies%20%5Ccfrac%7B~~%5Cfrac%7B7%7D%7B2%7D~~%7D%7Bm%7D%3D%5Ccfrac%7B~~1~~%7D%7B%5Cfrac%7B4%7D%7B3%7D%7D%5Cimplies%20%5Ccfrac%7B7%7D%7B2m%7D%3D%5Ccfrac%7B3%7D%7B4%7D%5Cimplies%2028%3D6m%20%5C%5C%5C%5C%5C%5C%20%5Ccfrac%7B28%7D%7B6%7D%3Dm%5Cimplies%20%5Ccfrac%7B14%7D%7B3%7D%3Dm%5Cimplies%204%5Cfrac%7B2%7D%7B3%7D%3Dm)
