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Current time:0:00Total duration:4:09

Video transcript

if the trip home takes 39 minutes at what time does Chris have to leave in order to be home by a quarter after 6:00 a quarter after 6:00 so let's draw a timeline and then think about what has to happen here this is at least how I need to visualize it in order to solve this problem and I'm going to do the hours before 6 and after 6 so I'll start at 5:00 and I'll go up to 7 just to make sure that we capture everything I can draw a straighter line than that so let me draw it a little bit straighter it's still not perfect but it'll do the job so let's say that this is 5 o'clock this is 6 o'clock and then let's specify whether it's AM or PM and this is 7 o'clock 7 o'clock they tell us he has to be home by a quarter after 6:00 so what is a quarter after 6:00 well it's going to be a quarter of the way between 6 & 7 o'clock so this would be half of the way between 6 & 7 o'clock and then a quarter would be half of that so this would be a quarter after 6:00 and if we wanted to specify what time a quarter after 6:00 is a quarter of the way between 6 & 7 we know there are 60 minutes in an hour so this distance is 60 minutes a quarter of 60 is 15 minutes so this time right over here is 6:15 and that's when Chris has to be home now they tell us that the trip home takes 39 minutes so he would have have to he would have had to have left 39 minutes before this in order to get home at 6:15 so let's go 39 minutes before this to figure out the time that he would have to leave in order to be home by 6:15 so what is 39 minutes what is 39 minutes before before 6:15 now the way my brain processes it I like to think about well how much time how much time does it take to get to the hour and then how much time do you have left to kind of go before the hour so this part right over here this part right over here is 15 minutes if you go back 15 minutes from 6:15 and go to 6 o'clock that was 15 minutes so we've already gone 15 minutes back if we go to 6 o'clock and then how many minutes do we have left to go back well we went 15 of the 39 39 minus 15 is 24 so we have to go another 24 minutes before the hour so this time right over here this time right over here is 24 minutes 24 minutes before before 6 o'clock before 6 o'clock and once again the way we figured it out well look going from 6:15 if you go 15 minutes back you get to 6 o'clock we have to go 39 so we have 24 left so then we have to go 24 minutes before 6 o'clock but 24 minutes before 6 o'clock would be how many minutes after 5 o'clock well once again we know that there are 60 minutes in an hour so what's 60 minus 24 let me do it right over here so 60 minus 24 is equal to 36 and you could either do that in your head or you could say hey look you know I could maybe borrow here this is a 10 this is 5 or regroup 10 minus 4 6 5 minus 2 is 3 the way my brain does it is I say oh you know 60 minus 30 would get me to 30 but then I have to subtract or 60 minus 20 would get me to 40 and then I need to subtract another 4 more to get to 36 but either way that if we're talking about 24 minutes before 6 o'clock that's the equivalent to 36 minutes minutes after after 5 o'clock so this time right over here is 5 5 36 so when they say what time does Chris have to leave in order to be home by a quarter after six five 36