Adding and Subtracting Time

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Adding and Subtracting Time
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Information about the video Adding and Subtracting Time

Contents

  • Addition and subtraction with time
  • Adding and Subtracting Time – Summary
  • ###Adding and Subtracting Time

    Freddie receives a letter from Zuri one day about a scavenger hunt. He needs to follow all of the clues to get a surprise at the end! However, he needs to make sure he gets to all of the clues in time for his surprise. In order to do this Freddie will need to add and subtract time intervals. Read more below, and you will learn about how to add and subtract time.

    Addition and subtraction with time

    How can you add and subtract hours and minutes with time? There are many different ways that you can add and subtract, one tool that you can use is a number line like the one below.

    Adding time to clock

    When adding time with a number line, always start by putting the starting number on the left. Next, skip count forward small amounts of the second addend. You can skip forward by fives, tens, or even larger amounts. Then, find the time that you landed on, this is the final time. You can use a number line when adding hours and when adding minutes

    Adding hours practice

    Freddie is looking for another clue from Zuri! He leaves at 2:20 to look and takes 35 minutes looking. What time does he finally find the clue? We can use an open number line to calculate this. Take a look at the open number line below, what time will Freddie find his next clue?

    24884_subtracting_Numberline_2_(1).svg

    If Freddie leaves at 2:10 and takes 35 minutes looking, he will find the next clue at 2:45

    Subtracting time from clock

    When subtracting time with a number line, always start by putting the starting number on the right. Next, skip-count backward small amounts of the second number. You can skip backward by fives, tens, or even larger amounts. Then, find the time that you landed on, this is the final time.

    Subtracting hours practice

    Freddie has been looking for clues all over! He needs to take a bus to get to the last clue by 5:30. Freddie needs to add and subtract time. If Freddie’s bus takes 25 minutes, what time should he leave so that he isn’t late? We can use an open number line to calculate this. Take a look at the open number line below, what time does Freddie need to leave by?

    24884_subtracting_Numberline_2_(1).svg

    If Freddie needs to be at the last clue by 5:30, and his bus takes 25 minutes to get there, Freddie should leave by 5:05.

    Adding and Subtracting Time – Summary

    Remember, when adding time…

    • Step one: Put the starting number on the left side of the open number line.

    • Step two: Count forward small amounts of the second number.

    • Step three: Where you land on the number line is the time.

    Remember, when subtracting time…

    • Step one: Put the starting number on the right side of the number line.

    • Step two: Count backward small amounts of the second number.

    • Step three: The number you land on is the time.

Transcript Adding and Subtracting Time

Freddie needs to be at the fountain to find the next clue, but what time will he get there? [Title] "Adding and Subtracting Time" It will take Freddie fourty-five minutes to get to the fountain. If he leaves at 1:15, what time will he get there? We can calculate this by adding time on a number line. When adding using a number line you always put the starting number on the LEFT side. Let's put 1:15 on the left side. Next we can hop forward small amounts of how much time it will take. It will take Freddie fourty-five minutes (...) so we can hop forward fourty-five minutes. We can skip count by tens to help. Ten (...) twenty (...) thirty (...) forty. Then, we can count five minutes more to find out the ending time. After skip counting forty-five minutes forward, we found the ending time (...) two o'clock. Freddie will get to the fountain at two o'clock. If it takes Freddie twenty minutes to get there, what time should he leave? We can help Freddie by using the number line to SUBTRACT time. When subtracting using a number line, you always put the starting number on the RIGHT side. Let's put 2:30 on the right side of the number line. Next, skip count backwards small amounts of the time it will take. Since it will take Freddie twenty minutes, we can skip count backwards twenty minutes. Let's skip count backwards by tens! Ten (...) twenty. We skip counted backwards twenty minutes and ended on 2:10. So, Freddie should leave by 2:10 to get there in time. [Freddie finds goggles and the next clue] If Freddie leaves right now at 2:30, what time will he get home after taking the two buses? We need to count up, or add, to find the answer. Since we’re adding, step one is to put the number on the LEFT side of the number line. Next, we need to skip count, or count up the amount of time it will take. If Freddie takes two busses that each take five minutes, when will he get home? [Pause for students to work] Freddie will get home by 2:40. [Freddie finding his floaties] The sunniest spot is close to the landfill, and it will take Freddie thirty-five minutes to get there Freddie needs to find Zuri by 3:30. If it takes him thirty-five minutes to get there, what time should he leave? We need to count backward, or subtract, to find the answer. Since we’re subtracting, we'll put the start time on the RIGHT side of the number line. Next, we'll skip count, or count backwards the amount of time it will take. If Freddie takes thirty-five minutes to find Zuri, and needs to get there by 3:30, when should he leave? [Pause for students to work] Freddie should leave by 2:55 in order to find Zuri in time! When ADDING with a number line, remember... Put the start time on the LEFT side. Next, skip count, or count forward on the number line. Then, skip count DOWN the number line until you reach the time. When SUBTRACTING time with a number line remember (...) Start by putting the time on the RIGHT side of the number line. Then, skip count, or count backwards small amounts on the number line until you reach the time. Remember, the number you count back to is the time.