9514 1404 393
Answer:
$70
Step-by-step explanation:
Four relationships are given among four unknowns. Define the following variables: p, c -- the cost of a pie and a cake, respectively. q, d -- the number of pies and cakes, respectively.
q/d = 5/2 . . . . . the ratio of pies to cakes sold
pq +cd = 3780 . . . . revenue from the sales
p = c -35 . . . . . a pie is $35 less than a cake
cd = pq -420 . . . . revenue from cakes is $420 less than for pies
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The equations are non-linear, so we're making up this process as we go along. We observe that 'pq' and 'cd' are involved in relations that give us their sum and difference, so these products are easily found. Their ratio can let us take advantage of our knowledge of q/d.
Substituting for cd in the second equation, we get ...
pq +(pq -420) = 3780
2pq = 4200
pq = 2100
cd = 2100 -420 = 1680
Now, we can write ...
pq/cd = 2100/1680 = 5/4
(p/c)(q/d) = 5/4 = (p/c)(5/2) . . . . substitute for q/d
p/c = 1/2 = (c -35)/c . . . . . . . . . . substitute for p
c = 2(c -35) . . . . multiply by 2c
c = 70 . . . . . . . . add 70-c
The cost of a cake is $70.
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<em>Additional comment</em>
24 cakes were sold at $70 each. 60 pies were sold at $35 each.
