Chapter Notes: Converting Units of Time
Time is something we measure every single day. We talk about how many minutes until recess, how many hours we sleep, or how many seconds it takes to run a race. But sometimes we need to change time from one unit to another. For example, if someone tells you a movie is 120 minutes long, you might want to know how many hours that is. Learning to convert units of time helps you understand and compare time measurements more easily. In this chapter, you will learn how to change between seconds, minutes, hours, days, and weeks.
Understanding Units of Time
Before we can convert units of time, we need to understand what each unit means and how they relate to each other. Time is measured in different units depending on how long something lasts.
The most common units of time we use are:
- Second - A very short amount of time. It takes about one second to say "one Mississippi."
- Minute - A longer amount of time made up of 60 seconds.
- Hour - An even longer amount of time made up of 60 minutes.
- Day - The time it takes for one full day and night, which is 24 hours.
- Week - A period of 7 days.
These units are connected to each other in specific ways. Knowing these connections is the key to converting from one unit to another.
Key Time Relationships
Here are the important relationships between units of time that you need to remember:
| Relationship | Equation |
|---|---|
| Seconds to Minutes | 60 seconds = 1 minute |
| Minutes to Hours | 60 minutes = 1 hour |
| Hours to Days | 24 hours = 1 day |
| Days to Weeks | 7 days = 1 week |
These relationships are like the rules of a game. Once you know them, you can change any time measurement into another unit.
Converting Larger Units to Smaller Units
When you convert from a larger unit to a smaller unit, you are breaking up a bigger piece of time into many smaller pieces. This means the number will get bigger. For example, 1 hour is the same as 60 minutes, so when we convert hours to minutes, the number goes up.
To convert from a larger unit to a smaller unit, you multiply.
Converting Minutes to Seconds
Since 1 minute equals 60 seconds, to convert minutes to seconds, we multiply the number of minutes by 60.
Example: Sarah timed how long she could hold her breath.
She held her breath for 2 minutes.How many seconds did Sarah hold her breath?
Solution:
We need to convert 2 minutes to seconds.
Since 1 minute = 60 seconds, we multiply:
2 minutes × 60 = 120 seconds
Sarah held her breath for 120 seconds.
Example: A song plays for 5 minutes.
How many seconds long is the song?
Solution:
We need to convert 5 minutes to seconds.
1 minute = 60 seconds
5 minutes × 60 = 300 seconds
The song is 300 seconds long.
Converting Hours to Minutes
Since 1 hour equals 60 minutes, to convert hours to minutes, we multiply the number of hours by 60.
Example: Marcus spent 3 hours reading a book on Saturday.
How many minutes did Marcus read?
Solution:
We need to convert 3 hours to minutes.
1 hour = 60 minutes
3 hours × 60 = 180 minutes
Marcus read for 180 minutes.
Converting Days to Hours
Since 1 day equals 24 hours, to convert days to hours, we multiply the number of days by 24.
Example: A camping trip lasted 2 days.
How many hours was the camping trip?
Solution:
We need to convert 2 days to hours.
1 day = 24 hours
2 days × 24 = 48 hours
The camping trip was 48 hours long.
Converting Weeks to Days
Since 1 week equals 7 days, to convert weeks to days, we multiply the number of weeks by 7.
Example: Summer vacation lasts 8 weeks.
How many days is summer vacation?
Solution:
We need to convert 8 weeks to days.
1 week = 7 days
8 weeks × 7 = 56 days
Summer vacation is 56 days long.
Converting Smaller Units to Larger Units
When you convert from a smaller unit to a larger unit, you are grouping many small pieces of time into fewer larger pieces. This means the number will get smaller. For example, 120 minutes is the same as 2 hours, so when we convert minutes to hours, the number goes down.
To convert from a smaller unit to a larger unit, you divide.
Converting Seconds to Minutes
Since 60 seconds equals 1 minute, to convert seconds to minutes, we divide the number of seconds by 60.
Example: A basketball player made a basket in 180 seconds.
How many minutes did it take?
Solution:
We need to convert 180 seconds to minutes.
Since 60 seconds = 1 minute, we divide:
180 seconds ÷ 60 = 3 minutes
It took 3 minutes to make the basket.
Example: A video is 240 seconds long.
How many minutes long is the video?
Solution:
We need to convert 240 seconds to minutes.
60 seconds = 1 minute
240 seconds ÷ 60 = 4 minutes
The video is 4 minutes long.
Converting Minutes to Hours
Since 60 minutes equals 1 hour, to convert minutes to hours, we divide the number of minutes by 60.
Example: Emma practiced piano for 120 minutes.
How many hours did Emma practice?
Solution:
We need to convert 120 minutes to hours.
60 minutes = 1 hour
120 minutes ÷ 60 = 2 hours
Emma practiced for 2 hours.
Example: A movie is 180 minutes long.
How many hours is the movie?
Solution:
We need to convert 180 minutes to hours.
Since 60 minutes = 1 hour, we divide:
180 minutes ÷ 60 = 3 hours
The movie is 3 hours long.
Converting Hours to Days
Since 24 hours equals 1 day, to convert hours to days, we divide the number of hours by 24.
Example: A road trip took 48 hours.
How many days was the road trip?
Solution:
We need to convert 48 hours to days.
24 hours = 1 day
48 hours ÷ 24 = 2 days
The road trip was 2 days long.
Converting Days to Weeks
Since 7 days equals 1 week, to convert days to weeks, we divide the number of days by 7.
Example: A project took 21 days to complete.
How many weeks did the project take?
Solution:
We need to convert 21 days to weeks.
7 days = 1 week
21 days ÷ 7 = 3 weeks
The project took 3 weeks to complete.
Multi-Step Time Conversions
Sometimes you need to convert between units that are not right next to each other. For example, you might need to convert hours to seconds, or weeks to hours. To do this, you break the problem into smaller steps, converting one unit at a time.
Converting Hours to Seconds
To convert hours to seconds, we need to go through minutes first:
- First, convert hours to minutes
- Then, convert minutes to seconds
Example: A science experiment takes 2 hours.
How many seconds does the experiment take?
Solution:
Step 1: Convert hours to minutes
2 hours × 60 = 120 minutes
Step 2: Convert minutes to seconds
120 minutes × 60 = 7,200 seconds
The experiment takes 7,200 seconds.
Converting Weeks to Hours
To convert weeks to hours, we need to go through days first:
- First, convert weeks to days
- Then, convert days to hours
Example: A summer camp lasts 2 weeks.
How many hours is the camp?
Solution:
Step 1: Convert weeks to days
2 weeks × 7 = 14 days
Step 2: Convert days to hours
14 days × 24 = 336 hours
The camp is 336 hours long.
Converting Seconds to Hours
To convert seconds to hours, we need to go through minutes first:
- First, convert seconds to minutes
- Then, convert minutes to hours
Example: A race took 7,200 seconds.
How many hours did the race take?
Solution:
Step 1: Convert seconds to minutes
7,200 seconds ÷ 60 = 120 minutes
Step 2: Convert minutes to hours
120 minutes ÷ 60 = 2 hours
The race took 2 hours.
Helpful Tips for Converting Time
Here are some tips to help you remember how to convert units of time:
- Multiply when going from larger to smaller units. The number gets bigger because you are breaking time into smaller pieces.
- Divide when going from smaller to larger units. The number gets smaller because you are grouping time into bigger pieces.
- Memorize the key relationships: 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day, and 7 days in a week.
- Use scratch paper. For multi-step conversions, write down each step so you don't get confused.
- Check your answer. Does your answer make sense? If you converted 3 hours to minutes, your answer should be bigger than 3.
Real-World Applications
Converting units of time is useful in many everyday situations. Here are some examples of when you might need to convert time:
- Cooking and baking: A recipe might say to bake cookies for 20 minutes, but your timer only shows seconds. You would need to convert 20 minutes to 1,200 seconds.
- Sports: A swim coach might time a race in seconds, but want to report the time in minutes and seconds.
- Travel planning: If you are taking a road trip that is 6 hours long, you might want to know how many minutes that is to plan rest stops.
- School schedules: If you have 45 minutes of reading time each day, you might want to know how many hours you read in a whole week.
- Screen time: If your parent says you can have 120 minutes of screen time, you might want to know that's the same as 2 hours.
Example: Lily practices soccer 3 times a week.
Each practice is 90 minutes long.How many hours does Lily practice soccer in one week?
Solution:
Step 1: Find the total minutes per week
3 practices × 90 minutes = 270 minutes per week
Step 2: Convert minutes to hours
270 minutes ÷ 60 = 4.5 hours
Lily practices 4.5 hours per week, which is the same as 4 hours and 30 minutes.
By learning to convert units of time, you can better understand time measurements and solve real problems. Whether you are timing a race, planning your day, or following a recipe, knowing how to change between seconds, minutes, hours, days, and weeks is a valuable skill that you will use throughout your life.
