Problem Solving

neeti2711 wrote:One millisecond is 0.001 of a second. The costs for a single run of a computer program are $1.07 for operating system overhead, $0.023 per millisecond of computer time, and $4.35 for the mounting of a data tape. What is the total of these three costs for 1 run of a program that requires 1.5 seconds of computer time?

(A) $7.15
(B) $8.87
(C) $28.96
(D) $35.57
(E) $39.92

Let's first determine the cost of 1.5 seconds of computer time. To do so, we can use equivalent ratios.

Here, we are comparing cost and time. So, the ratio is (cost in dollars)/(time in seconds)

We're told that computer time costs $0.023 per millisecond of computer time. Since a millisecond = 0.001, we can write the ratio:
(0.023)/(0.001)

The decimals here create a problem, so let's create an equivalent ratio by multiplying top and bottom by 1000 to get: (23)/(1)
This tells us that it costs $23 for 1 second of computer time.

From here, if we multiply top and bottom by 1.5, we get: (34.5)/(1.5)
This tells us that it costs $34.50 for 1.5 seconds of computer time. Great!

So, the total cost = $34.50 + $1.07 + $4.35 = $39.92 = E

Cheers,
Brent