
Andrew M. answered 03/24/18
Tutor
New to Wyzant
Mathematics - Algebra a Specialty / F.I.T. Grad - B.S. w/Honors
Let p = number persons originally attending
Let c = original cost per person
Number of persons will be the total cost of 2520 divided by the original cost per person, c:
p = total/(cost per person)
p = 2520/c {equation 1}
When the number of persons decreased by 4, the cost per person increased by 224:
p-4 = 2520/(c+224) {equation 2}
Replace p with 2520/c in equation 2 and solve for c:
2520/c - 4 = 2520/(c+224)
Get common denominator on left side
(2520 - 4c)/c = 2520/(c + 224)
Cross multiply
2520c = (2520-4c)(c + 224)
Distribute the parenthesis on the right side with FOIL
2520c = 2520c + 2520(224) - 4c2 - 896c
Subtract 2520c from both sides
0 = -4c2 - 896c + 564480
For ease of working I multiplied both sides by -1
4c2 + 896c - 564480 = 0
All numbers are factorable by 4 so divide both sides by 4
c2 + 224c - 141120 = 0
Using quadratic equation: Given ax2 + bx + c = 0
x = [-b ±√(b2-4ac)]/2a
c = [-224 ±√(2242-4(-141120))]/2
c = (-224 ±√614656)/2
c = (-224 ± 784)/2
Disregarding the negative since the cost will be a positive quantity:
c = (784-224)/2
c = 560/2
c = 280 The original cost per person was RM 280
p = 2520/c = 2520/280 = 9 Originally 9 persons were supposed to go
4 cancelled meaning 5 persons actually went