Question Video: Applying Operations on Time Using a Digital Clock | Nagwa Question Video: Applying Operations on Time Using a Digital Clock | Nagwa

# Question Video: Applying Operations on Time Using a Digital Clock Mathematics • Third Year of Primary School

Mason wants to meet his friends at the park at 4 o’clock. It will take him 15 minutes to walk there. What time does he need to leave his house?

02:24

### Video Transcript

Mason wants to meet his friends at the park at 4 o’clock. It will take him 15 minutes to walk there. What time does he need to leave his house?

We know that Mason needs to be at the park at 4 o’clock, and we know it takes him 15 minutes to walk there. We could use a number line to help us solve this problem. We know that Mason needs to be at the park by 4 o’clock. Let’s call this the end time. We also know that his walk will take him 15 minutes. So, we need to use the number line to find out what time it was 15 minutes ago. We need to count back 15 minutes.

We know that halfway between 3 and 4 o’clock, it’s 3:30. Halfway between 3:00 and 3:30 is 3:15. And halfway between 3:30 and 4 o’clock, it’s 3:45 or quarter to four. So, let’s start at 4 o’clock and count back 15 minutes. Each of the smaller divisions on our number line is worth five minutes. If we count back five minutes, that will take us to 3:55 or five minutes to 4 o’clock. There are 60 minutes in an hour. So, if we take away five minutes, we’re at 3:55. If we count back five minutes from 3:55, that will take us to 3:50. Five minutes less than 3:50 is 3:45. So, Mason needs to leave his house at 3:45.

We can check our answer using a model of a clock. The minute hand started at number 12, and we had to count back 15 minutes or three lots of five: five, 10, 15. So, if Mason needs to meet his friends at 4 o’clock and it takes him 15 minutes to walk to the park, he will need to leave his house at 3:45.

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