In real life, it is very useful to be able to work out how long it takes for something to happen, or the actual time when something will take place.

Remember that there are **60 minutes** in an hour.

**Adding or subtracting minutes**

Adding or subtracting minutes to or from a time can be simple.

15 minutes before 7:30 p.m. is simply 7:15 p.m.

15 minutes after 7:30 p.m. is simply 7:45 p.m.

Be careful when you have to cross a whole hour.

Go to the whole hour first and then go on.

15 minutes before 7:10 p.m. is 6:55 p.m.

(Go back 10 mins to 7 o'clock and then 5 mins further back.)

15 minutes after 7:50 p.m. is 8:05 p.m.

(Go forwards 10 mins to 8 o'clock and then 5 mins more.)

**Example**

A TV programme starts at **4:25 p.m. **and ends at **6:10 p.m.**

How long does it last?

**Answer**

From 4:25 p.m. to 5 o'clock is 35 mins.

From 5 o'clock to 6 o'clock is 1 hour.

From 6 o'clock to 6:10 p.m. is 10 mins.

35 mins + 10 mins + 1 hour =** 1 hour and 45 mins.**