Problema Solution
A person hired to build a CB radio tower. The firm charges $100 for labor the first 10 feet. After that, the cost of the labor for each succeeding 10 feet is $25 more than the preceding 10 feet. That is, the next 10 feet will cost 125, the next 10 feet will cost $150, etc. How much will it cost to build a 90 foot tower.
Answer provided by our tutors
N= number of terms altogether
D= common difference
A1 = first term
An = last term
N= 9 which is how many terms or repeated additions will be used
D= $25 which is the price added to the previous price
A1= $100 which is the initial cost for this project.
An = a9
aN = a1 + (n-1)d
a9 = 100 + (9-1)25
a9= 100 +8(25)
a9= 100 + 200
a9= 300
The formula I will be using is
Sn= n(a1+aN)
2
Sn= 9(100 + 300)
2
Sn = 9(400)
2
Sn = 4.5(400) = 1800
The total amount needed to build a 90 foot tower would be $1,800