By Chutima S (Dr.เยลลี่)
Published: 27 Aug. 2025
Addition and subtraction of time is another essential skill that children must learn early in their elementary math studies. We use it in daily planning and time management, such as calculating how many minutes it takes to travel to school, how many hours remain before an appointment, or how many minutes are left until lunchtime. Understanding this topic helps students build confidence in elementary math.
Before being able to add or subtract time correctly, it is necessary to first understand the units of time, such as:
Once these units are understood, we can add or subtract time within the same units, such as combining the time spent on activities or finding out how many minutes/hours separate two events. Practicing this is a form of elementary math exercises that helps children develop both analytical thinking and time management skills 💡
When adding time, write it separately as hours – minutes – seconds in a table. Arrange the smallest unit on the right and prepare a space above for carrying over.
Write hours – minutes separately in a table, and prepare a space above for carrying over.
Start by adding the minutes on the right-hand side first.
75 minutes = 1 hour 15 minutes
Carry over 1 to the hours, and write 15 in the minutes column
Add hour
The answer is 2 hours 15 minutes
Subtracting time is similar to addition. Write the values separately as hours – minutes – seconds in a table, placing the smallest unit on the right and prepare a space above for “borrowing”.
Find 2 days 3 hours $-$ 15 hours
Write days – hours separately in a table, and prepare a space above for borrowing.
3 hours is not enough to subtract 15 hours, so you need to borrow.
2 days $=$ 1 day 24 hours → add 24 hours to the original 3 hours, making 27 hours
Subtract the hours on the right-hand side using the 27 borrowed hours.
Subtract Day
The answer is 1 day 12 hours
Adding and subtracting time not only helps children calculate correctly, but also trains them to think analytically, organize events in order, and manage their time effectively ✨. Children who understand this concept will be able to plan their studies, activities, and daily life more efficiently.
At MJ, we provide free elementary math articles like this for students and parents to strengthen understanding. But if you’d like continuous learning with real practice exercises, our online elementary math tutoring system and one-on-one math courses with personal math teachers will give your child individual support. Whether it’s preparing for entrance exams into secondary school or private math lessons at home, MJ helps build a strong foundation and makes learning math more enjoyable 🚀 Try learning with MJ and see the difference yourself!