William S. answered 12/16/13
Experienced scientist, mathematician and instructor - William
Let NA be the number of adult tickets sold and NC be the number of child tickets sold.
We know that NA + NC = 240. (Eq. 1)
We also know that ($15)*NA + ($9)NC = $3060. (Eq. 2)
We have a choice of how to proceed. We can either solve Eq. 1 for NA and substitute that value into Eq. 2, or we can solve Eq. 1 for NC and substitute that value into Eq. 2.
Let's do it the first way mentioned:
NA = 240 - NC
Eq. 2 then becomes:
($15)(240 - NC) + ($9)(NC) = $3060
We now have one equation with one unknown (NC).
($15)(240) - ($15)(NC) + ($9)(NC) = $3060
$3600 - 6NC = $3060
-6NC = -$540
NC = 90
If NC = 90, then NA = 240 - 90 = 150
Let's see if our answer makes sense:
Does (NC)($9) + (NA)($15) = $3060?
Does (90)($9) + (150)($15) = $3060?
YES!
12/13/2013 | William S.
Parviz F.
12/16/13