David W. answered 08/02/15
Experienced Prof
This problem, like a document yet to be spell-checked, has a typo. Now, spell-check and grammar-check can autocorrect or suggest a correction (and AI is even better than that). Using probabilities, we start by assuming the cost of tickets ($5, $10, $15) is likely correct, then the relationship of the sum of $5 and $10 tickets to the number (note: “amount” is ambiguous) of $10 tickets is correct. So, that leaves possible errors in the number of tickets or else the total of the money.
Tutors (and computers) can easily calculate values both ways and conclude that “positive integer amounts” of tickets and cents are required (assume: correct accounting but typo in reporting college function information). So, $19,000 is better than 180 tickets [calculate it!] (or other typos).
Let:
V = Number of $5 tickets
X = Number of $10 tickets
F = Number of $15 tickets (I like single letters, so think some Roman Numerals)
Thus, the problem has “givens:”
V + X + F = 1800 (eq1)
5V + 10X + 15F = 19000 (eq2)
V + F = 2X (eq3)
Use elimination method (eq1 – eq3):
-X = 2X – 1800
-3X = -1800 (subtract 2X from both sides)
X = 600 (divide both sides by -3)
Now, we must use eq2, so calculate ( eq2 - 5*eq3):
5V + 10X + 15F = 19000
5V - 10X + 5F = 0 (modified eq3)
------------------------------------------
20X + 10F = 19000
12000 + 10F = 19000 (using X=600)
10F = 7000 (subtract 12000 from both sides)
F = 700
Now, using eq1:
V + 600 + 700 = 1800
V = 500 (subtract 1300 from both sides)
Checking (very important):
Is 500 + 600 + 700 = 1800 ? yes
Is 5(500) + 10(600) + 15(700) = 19000 ?
2500 + 6000 + 10500 = 19000 ? yes
Is 500 + 700 = 2(600) ? yes
David W.
08/02/15
Linda C.
08/02/15