Bunuel wrote:
During the first week in May, a video salesman sold n videos at an average (arithmetic mean) commission of z dollars per video. During the next week, the same salesman sold n – 4 videos at an average commission of $15 less than the week before. What is the difference in total commissions from the first week to the second week in terms of n and z?
A. nz – 60
B. n^2 – z + 60
C. 2nz – 15z +60
D. 4z + 15n – 60
E. 4z + 60
Attachment:
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Algebra\(A*n = S\)• Week 1
A = z
n = n
SUM = nz
• Week 2
A = (z - 15)
n = (n - 4)
SUM = (n - 4)(z - 15)
For Week 2 SUM, multiply terms A*n
(n - 4)(z - 15)
SUM = (nz - 25n - 4z + 60)
• DIFFERENCE between Week 1 SUM and Week 2 SUM?
nz - (nz - 25n - 4z + 60) =
nz - nz + 25n + 4z - 60 =
25n + 4z - 60, or
4z + 25n - 60
Answer D
Assign valuesLet Week 1 number of videos sold,
n = 6Let Week 1 average price of video,
z = $20Week 2 number of videos sold is (n-4),
n = 2Week 2 average price per video is (z-15), ($20 - 15) =
z = $5• Week 1 SUM, where A*n = S
($20 * 6) = $120
• Week 2 SUM
($5 * 2) = $10
• Difference between Week 1 sum and Week 2 sum:
$120 - 10 = $110
•
Using n = 6, z = 20, find the answer choice that yields 110A) nz – 60
120 - 60 = $60. NOT A MATCH
B) n^2 – z + 60
36 - 20 + 60 = 76. NOT A MATCH
C) 2nz – 15z +60
2(120) - (15)(20) + 60
240 - 300 + 60 = 0. NOT A MATCH
D) 4z + 15n – 60
80 + 90 - 60 = 110. MATCH
E) 4z + 60
80 + 60 = 140. NOT A MATCH
Answer D