Addition and Subtraction of Time

Addition and Subtraction of Time

Addition and subtraction of time are important topics in maths that help students understand how to calculate time easily while solving questions and in real life as well. While doing addition of time, you combine hours and minutes to know the total time. On the other hand, when you do subtraction of time, it is important to find how much time has passed or how much time is left.

Learning addition and subtraction of time helps students plan their day better and solve time-related problems quickly in exams. Once you understand this concept well, it becomes easy for you to solve adding time word problems. Keep reading to learn more about the addition and subtraction of time, along with solved examples.

Read More: Adding and Subtracting of Rational Numbers

Time and Its Units

Before we learn addition and subtraction of time, it is important to understand what time is and its basic units. Time is measured in different units. The most common units are seconds, minutes, hours, days, months, and years. Smaller units also exist, like milliseconds and microseconds.

Knowing these basic units of time is important when doing addition of time or subtraction of time, because you often need to convert one unit into another to solve problems correctly. Here are some basic conversions:

• 1 day = 24 hours

• 1 hour = 60 minutes

• 1 minute = 60 seconds

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Addition and Subtraction of Time: Conversions Between Hours, Minutes, and Seconds

To do addition and subtraction of time, it is important to know how to convert between hours, minutes, and seconds. These conversions help you solve addition and subtraction of time word problems asked in exams accurately.

How to Convert Between Hours, Minutes, and Seconds?

Here are a few time-related formulas that you can use to convert between hours, minutes, and seconds:

• Time in seconds = time in minutes × 60 = time in hours × 3600

• Time in minutes = time in seconds ÷ 60 = time in hours × 60

• Time in hours = time in minutes ÷ 60 = time in seconds ÷ 3600

Read more: How to Subtract With and Without Borrowing

Addition of Time

Addition of time means adding hours, minutes, and seconds together in order to find the total time. This is very useful when you want to know how much time two or more activities take together. Here are some steps you can follow for doing the addition of time:

• Add the hours of the given times.

• Add the minutes of the given times.

• Convert if needed: If the total minutes are 60 or more, convert the extra minutes into hours. For example, 75 minutes = 1 hour 15 minutes.

By following these steps, you can easily solve adding time word problems without confusion. Let's see some examples here:

Examples of Adding Time Word Problems

Example 1: Ravi starts reading a book at 2:15 PM. He reads for 1 hour and 40 minutes. At what time will he stop reading?

Solution:

• Step 1: Add the hours: 2 + 1 = 3 hours

• Step 2: Add the minutes: 15 + 40 = 55 minutes.

• Step 3: Combine hours and minutes: 3:55 PM

Hence, Ravi will stop reading at 3:55 PM.

Example 2: A movie starts at 4:20 PM and lasts 2 hours and 35 minutes. What time does the movie end?

Solution:

• Step 1: Add the hours: 4 + 2 = 6 hours

• Step 2: Add the minutes: 20 + 35 = 55 minutes

• Step 3: Combine hours and minutes: 6:55 PM

So, the movie ends at 6:55 PM.

Read More: 2 Digit Subtraction

Subtraction of Time

Subtraction of time is used for finding the difference between two times. It is very similar to the addition of time and helps us know how much time has passed or is left. Here is how you can do subtraction of time:

• First, subtract the hours of the given times.

• Next, subtract the minutes. If the minutes of the second time are greater than the first, borrow 1 hour and add 60 minutes before subtracting.

Addition and Subtraction of Time Word Problems

Addition and subtraction of time word problems given here help you practice questions where you need to calculate the total time or the difference between times.

Word Problem 1: Rama started practicing guitar at 3:30 p.m. He practiced until 5:55 p.m. For how long did he practice?

Solution:

• Step 1: Subtract the hours: 5 - 3 = 2 hours

• Step 2: Subtract the minutes: 55 - 30 = 25 minutes

• Hence, Rama practiced for 2 hours 25 minutes.

Word Problem 2: Mr Roy started his walk at 11:03 a.m. He took a break at 12:29 p.m. How long did he walk?

Solution:

• Step 1: Subtract the hours: 12 - 11 = 1 hour

• Step 2: Subtract the minutes: 29 - 3 = 26 minutes

• So, he walked for 1 hour 26 minutes.

Word Problem 3: Monu started his test at 8:45 a.m. The test lasted 1 hour 24 minutes. At what time did he finish?

Solution:

• Step 1: Add the hours: 8 + 1 = 9 hours

• Step 2: Add the minutes: 45 + 24 = 69 minutes. Convert 69 minutes: 1 hour 9 minutes

• Step 3: Add the extra hour to the total hours: 9 + 1 = 10 hours

• Hence, Monu finished the test at 10:09 a.m.

Word Problem 4: Riya started playing a game at 3:20 p.m. She played for 2 hours 35 minutes. At what time did she stop playing?

Solution:

• Step 1: Add the hours: 3 + 2 = 5 hours

• Step 2: Add the minutes: 20 + 35 = 55 minutes

• Hence, Riya stopped playing at 5:55 p.m.

Also read: Substitution Method

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