Time

19 years, two months

From 7 a.m. to 1:30 p.m. there are 6 hours and 30 minutes.

It is 3:15pm.

15 minutes is one quarter of an hour.

17 hours and 54 minutes.

00:05

8 hours and 30 minutes.

8 hours.

It is: 46.875%

12am to 4pm is 16 hours.

3 minutes short of 3 hours

180 - 3 = 177

2 hours 57 minutes

60 + 60 + 57 = 177

It is 55 hours and 12 minutes.

An 83.33% decrease.

2,800 minutes = 1day 22hrs 40mins

There are 1 60th of an hour in 1 minute, as there are 60 minutes in 1 hour.

1:01 am

Depends on how you mean. Accurate timing wasn't as important earlier, which meant that getting it a little wrong didn't matter much. And if being a bit wrong doesn't matter, then measuring becomes easier. OTOH, clocks and watches were cruder too. If you really wanted to time an event accurately, it would have been more difficult. Today OTOH, even a basic wristwatch can measure down to the 1/100 of a second. We have both better tools to measure time, but also much greater need to measure time accurately.

A decasecond is equal to 10 seconds. Therefore, there are 10 seconds in a decasecond.

There are not.

1 nano second = 10^-9 second → 1 s = 10^9 ns.

There are 3600 seconds in 1 hour → 1 hour = 3600 s = 3600 × 10^9 ns = 3.6 × 10^12 ns.

It is: 1/3 of 60 = 20 minutes

9 hours 45 minutes

There are 86400 seconds.

267 = 60 + 60 + 60 + 60 + 27

so 4 hours 27 minutes

It is 14 milliseconds.

It is 2 + 24*k hours where k is an integer.