Question

Skyscraper Windows

Answer 1

Answer:

A.) $2,166

B.) $10,545

C.) (n/2)(3.5 + 0.5n) × 38

Step-by-step explanation:

Floor - - - - - - - - - - 1 - - - - - - - 2 - - - - - - - 3

Cost / window - - $2.00 - - - $2.50 - - - $3.00

Cost of washing first floor = $2 × 38

Cost of second floor is: (2 + 0.5) × 38

Cost of third floor is: (2 + 2 × 0.5) × 38

Cost of n floor : (2 + (n - 1) × 0.5) × 38

Therefore,

Total cost :

(2 + (2 + 0.5) + (2 + 2*0.5) + ... + (2 + (n - 1)*0.5)) × 38

Using Arithmetic progression for the sequence :

2, (2 + 0.5), (2 + 2*0.5),..., (2 + (n - 1)*0.5)

first term 'a' = 2; common difference 'd' = 0.5

Sum of the first n terms of arithmetic sequence terms is:

S = (n/2)(2a + (n - 1)d) ; Where a = 2 and d = 0.5

S = (n/2)(2*2 + (n - 1)*0.5)

S = (n/2)(4 + 0.5n - 0.5)

S = (n/2)(3.5 + 0.5n)

To wash all windows with n stories :

S × 38 windows

A.) To wash all windows : stories = 12

n = 12

(12/2)(3.5 + 0.5(12)) × 38

6(3.5 + 6) × 38 = $2,166

B.) if building is 30 stories tall:

n = 30

(30/2)(3.5 + 0.5(30)) × 38

15(3.5 + 15) × 38 = $10,545

C.) If building is n stories tall :

(n/2)(3.5 + 0.5n) × 38