How to Find the Subtraction in Time?
Time is a varying factor. In a day, we have 24 hours, 1440 minutes, and 86400 seconds. Now, to calculate the time difference, we use the subtraction operator. For example, if Neha started her journey at 10:00 a.m. and reached her home at 12:00 p.m., what was the time difference between Neha’s journey from home to office, and vice versa? Well, it's 12: 00 − 10: 00 = 2hrs. This means that Neha took two hours to reach her office.
Similarly, we can find the time subtraction across various journeys. So, let us understand these with the help of illustrating examples.
Examples of Time Addition and Subtraction
Before starting with the difference in time, let us see the addition of time:
Example: Add 4:45 and 3:10.
Solution: On adding 4 and 3, we get 7 and 45 + 10 gives 55. So, we have 7:55.
Now, let us take another example:
Example: Add 5:50 and 4:30.
Solution: On adding 5 and 4, we get 9. Also, on adding 50 and 30, we get 80.
Here, we can see that 80 > 60. We can write 80 as 80 = 60 + 20. This means 80 minutes is 1 hr and 20 minutes.
Here, 9 hrs + 1 hr + 20 minutes is equal to 10 hrs 20 minutes or 10:20 is our answer.
Now, if we wish to find the difference between 5:50 and 4:30, we have the following steps:
5 − 4 = 1 hr
50 − 30 = 20 minutes
Here, the difference or the time subtraction comes out to be 1 hr 20 minutes or 1:20.
Time Subtraction Solved Examples
Example 1: Subtract 3:45 and 1:14.
Solution:
Subtraction of hours: 3 − 1 = 2 hours
Subtraction of minutes: 45 − 14 = 31 minutes
So, 2 hrs 31 minutes is the answer.
Example 2: Subtract 4:10 and 6:15.
Solution:
Subtraction of hours: 4 − 6 = −2
Subtraction of minutes: 10 − 15 = −5
Here, we can see that hours is less than 0, so we have:
− 2 + 24 = 22
Adding 60 to minutes: − 5 + 60 or 60 − 5 = 55 Minutes
Hence, the time subtraction for 4:10 and 6:15 comes out to be 21:55.
FAQs on Find the Subtraction in Time
1. How do you subtract time in hours and minutes?
To subtract time, you first subtract the minutes, and then you subtract the hours. If the minutes in the first time value are less than the minutes in the second, you must borrow 1 hour from the hour column and add 60 minutes to the minute column before subtracting.
2. What is the method for subtracting time when borrowing is needed, for example, 5 hours 20 minutes - 2 hours 50 minutes?
When the minutes you are subtracting are larger (e.g., 50 min > 20 min), you must borrow from the hours. Here’s the step-by-step method:
- Step 1: Borrow 1 hour from the '5 hours', leaving you with 4 hours.
- Step 2: Convert that borrowed hour into 60 minutes and add it to the existing minutes: 20 + 60 = 80 minutes.
- Step 3: Your problem is now: 4 hours 80 minutes - 2 hours 50 minutes.
- Step 4: Subtract the minutes (80 - 50 = 30) and the hours (4 - 2 = 2). The final answer is 2 hours and 30 minutes.
3. How can I calculate the time duration between a start time and an end time?
To find the elapsed time, you simply subtract the start time from the end time. For calculations that cross from a.m. to p.m., it's easiest to convert the times to a 24-hour format first. For instance, to find the time between 9:00 a.m. and 2:00 p.m., convert 2:00 p.m. to 14:00. Then subtract: 14:00 - 9:00 = 5 hours.
4. Why do we borrow 60 minutes instead of 100 when subtracting time?
We borrow 60 because time measurement is not based on a decimal system (like our money). It uses a sexagesimal system, which is based on the number 60. There are 60 seconds in a minute and 60 minutes in an hour. Therefore, when you borrow '1' from the hour column, you are actually borrowing one full hour, which is equal to 60 minutes.
5. How do you subtract time that crosses over midnight, like finding the time 5 hours before 2:00 a.m.?
To subtract time across midnight, you work backwards. Let's find the time 5 hours before 2:00 a.m.:
- First, go back 2 hours from 2:00 a.m. This brings you to 12:00 a.m. (midnight).
- You still need to go back another 3 hours (because 5 - 2 = 3).
- Counting back 3 hours from midnight brings you to 9:00 p.m. on the previous day.
6. What is the main difference between subtracting time in a 12-hour (a.m./p.m.) format and a 24-hour format?
The key difference is simplicity and clarity. In the 24-hour format, subtraction is a straightforward mathematical operation because time progresses linearly from 00:00 to 23:59. In the 12-hour format, you must mentally manage the switch between a.m. and p.m., which can be tricky when calculating durations that cross noon or midnight. Converting to the 24-hour format is often the most reliable method for complex subtractions.
7. Besides schoolwork, where is subtracting time a useful skill in real life?
Subtracting time is a fundamental life skill used in many daily situations. Examples include:
- Calculating the duration of a journey, such as a flight or train trip.
- Figuring out how much time you spent on a specific task to manage your study schedule.
- Timing a recipe while cooking.
- Calculating the length of a movie or a sports event.
- Checking how much time is left on a parking meter.
