Question

Noelle and Micah went to the bank to open new checking accounts. The equation C=0.2n+1.20 represents the monthly cost, C, in dollars, where n is the number of checks written by Noelle. In Micah's account, the monthly cost is proportional to the number of checks written. The monthly cost for Micah's account is $1.20 for writing 3 checks. How many checks must Noelle and Micah write, if any, so that the cost of the accounts is the same for one month? What is the cost, if any?

Answer 1

C = $2.40

n = 6

Explanation:

For Noelle,

Equation that represents the monthly cost 'C',

C = 0.2n + 1.20

Here, n = number of checks written in a month

For Micah,

Monthly cost for writing checks 'C' = $1.20

Number of checks 'n' = 3

Since, Cost of writing checks ∝ Number of checks written

C' ∝ n

C' = kn

k =
`(C')/(n)`

Here, k = proportionality constant

For C' = 1.2 and n = 3

k =
`(1.2)/(3)`

k = 0.4

Equation will be,

C' = 0.4n

For any month C = C'

Therefore, 0.2n + 1.20 = 0.4n

0.4n - 0.2n = 1.20

0.2n = 1.20

n = 6

Number of checks written by Noelle and Micah = 6

For n = 6,

C = 0.2(6) + 1.20

C = $2.40

Cost of writing checks = $2.40