Business and finance. Avirus scanning program is checking every file for viruses.

It has completed checking 40% of the files in 300 seconds. How long should it take
to check all the files?

if you add another 40%, you will be done with 80% in 600 seconds. 20% is left. .20 times 600=120 sec

600+120=720 sec

Jen is wrong.

A simple test of taking 40% of her answer of 720, which would be 288, would have indicated it was not right

let the total time be x seconds
so .4x = 300
x = 300/.4 = 750 seconds

(check: 40% of 750 = 300)

To find out how long it should take to check all the files, we can use the concept of proportions. Let's break down the given information:

- The virus scanning program has completed checking 40% of the files in 300 seconds.
- We need to find out how long it will take to check 100% of the files.

To solve this problem, we can set up a proportion. The proportion will compare the amount of time it took to check 40% of the files to the amount of time it will take to check 100% of the files.

Let's set up the proportion:
40% of the files / 300 seconds = 100% of the files / x (unknown time in seconds)

To solve for x, we can cross-multiply and then divide:
(40% of the files) * x = (100% of the files) * 300 seconds

Now, let's plug in the values and calculate:
0.4x = 1 * 300
0.4x = 300
x = 300 / 0.4
x = 750

Therefore, it should take 750 seconds (or 12.5 minutes) to check all the files.