TIME MATH 

Did you ever have to figure out what time you have to get up in the morning? If you have to get to school by 8:00 A.M. and it takes you 45 minutes to get dressed, eat your breakfast and drive to school, what time should you get up in the morning? 

If you get out of school at 2:30 P.M., and it takes 35 minutes to get to you music teacher’s house, will you be late for your 3:00 P.M. lesson? 

Here is how to do time math: 

Addition: 

2:30 + 35 minutes = 2:65. But there is no 65 on the clock. There are only 60 minutes in an hour. So subtract 60 from 65. Add that hour to the 2. The answer is 3:05. 

If we add the minutes, and the result is greater than 60, subtract 60 from the answer. Then add 1 to the hour, and the remainder is the minutes. 

If the hour in the answer is greater than 12, subtract 12. In our country, we use A.M and P.M., so if we have to subtract 12, we change the A.M. to P.M., or P.M. to A.M. 

Here is an example: 

It is 3:15 P.M. What time will it be in 2 hours and 55 minutes? 

First, we add the hours:  3 + 2 = 5

Second, we add the minutes: 15 + 55 = 70 minutes.

The minutes answer is greater than 60, so we subtract 60 from the 70, leaving 10 minutes.

Finally, we add 1 hour to the answer in step 1: 5 + 1 = 6 

The answer is: 6:10 P.M. 

Here’s another example: 

It’s 11:30 A.M. What time will it be after you 1 hour and 45 minute lunch period? 

First, add the hours: 11 + 1 = 12

Second, add the minutes: 30 + 45 = 75

Third, subtract 60 minutes from 75, leaving 15

Fourth, add the 1 hour to 12 = 13

The time will be 13:15 

In some countries, that is the time they use. In our country, we subtract 12 from the 13, and change A.M. to P.M. 

The time will be 1:15 P.M.

 Subtraction 

If it takes 45 minutes to get ready for school, what time should we get up if our bus leaves at 8:00 A.M.? 

We subtract 45 minutes from 8:00. But we notice that there are no minutes in 8:00.

So we take 1 hour from the 8 and change it into 60 minutes. So the time is 7:60.

Now we can subtract the 45 minutes from the 60 minutes leaving 15 minutes.

We have to get up at 7:15 A.M. 

Here is a hard one. 

You have to be home by 1:00 P.M. It will take you 90 minutes to walk home. What time should you start walking?

First, we change the 90 minutes to 1 hour and 30 minutes. Remember, there are 60 minutes in an hour. Now we are going to subtract 1:30 from 1:00. Since, we can’t subtract 30 from 0; we need to change 1 hour into 60 minutes. But if we take 1 hour from 1:00, we will have 0:00 P.M. But, this is the same as 12:00 noon.  

So we are now subtracting 1 hour and 30 minutes from 12:60.

We subtract the hours: 12 – 1 = 11.

Now we subtract the minutes: 60 – 30 = 30.

The answer is: 11:30.

One last step. Since we went past 12:00 we have to change the P.M. to A.M.

So the answer is we have to start walking home by 11:30 A.M.