If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:3:32

Video transcript

a went running four days this past week he ran nine kilometers on each day in that same week Beth ran 15 fewer kilometres than Abe how many kilometers did Beth run that week so I encourage you to pause this video and to try this on your own try to figure out how many kilometers did Beth run that week so there's a couple of ways to think about it or a couple of ways to visualize it the first thing we might might want to do in fact the first thing we definitely want to do is to figure out well how far did a run in that week well he went four days and each day he went nine kilometers so we could say that he went four days times in that blue color four days times nine kilometers per day and we could visualize that so this is how much she went in one day this is how much she went in two days this is how much he'd go in three days this is how much she would go in four days so what is this what is four what is four times nine kilometers well this is essentially nine plus nine plus nine plus nine so we could just add up the nines 9 plus 9 is 18 plus 9 is 27 plus 9 is 36 so he ran a total of 36 kilometers so he ran a total of 36 kilometers now that's not what they're asking us for they're asking us for the number of kilometers Beth ran that week and they tell us that she ran 15 fewer kilometers than Abe so this right over here Abe's total distance if we start from here and we were to go all the way all the way over the week all the way to here he ran 36 total kilometers Beth ran 15 fewer kilometers than Abe so let's go back 15 kilometers so back 15 kilometers so Beth ran 15 fewer fewer kilometers fewer kilometers than Abe so that's 15 fewer kilometers and so the number that Beth ran the number of kilometers that Beth ran would be this distance it would be this distance right over here so this is kilometres Beth ran kilometers or bets let me write this Beth's Beth's distance in the week Beth's distance would be this distance right over here so how do we figure that out well if we say bets distance let's just use the letter B for shorthand so Beth's distance plus 15 kilometres plus 15 kilometres is going to be equal to Abe's distance is going to be equal to 36 kilometres or another way of thinking about it BET's distance that's distance is going to be equal to Abe's distance so 36 kilometers 30 six kilometers - 15 - 15 - 15 so what is Beth's distance going to be equal to well 36 minus 15 six minus five is 130 minus 10 is 20 so it's going to be 21 so Beth's distance is 21 kilometers