Antonia likes calculating the sum of the digits that she sees on
her digital clock. For example, if the time were 11:47, the sum
would be equal to 13 (1+1+4+7). What is the largest sum she can
get on a 12-hour digital clock?

23

Step-by-step explanation:

The 12 hour clock doesn't go past 12 on the first 2 digits (hour).

The 24 hours goes 13:, 14:, 15: and so on.

We now have to figure out "4" largest numbers on the 12-hr clock and add them to get the max sum out of them.

The hours are:

00

01

02

...

09

10

11

12

The largest sum would be that of "09"

Now, the minutes:

59 is the highest minute and that will give us the highest sum

So, the time we are looking for is:

09:59

The sum is:

0 + 9 + 5 + 9 = 23