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Main content
Current time:0:00Total duration:6:44

Telling time with number line

CCSS.Math:

Video transcript

Andrey Andrey Andrey starts working on his science project at 4 o'clock p.m. and he finishes 50 minutes later which number line below has a red dot marking when Andrey finishes working on his science project so they tell us that he starts his science project at 4 o'clock p.m. this first shot this first choice over here puts the dot at 4 o'clock but they didn't say when did he start working on his science project they say put a red dot marking when Andrey finishes working on his science project so he started at 4 and it says he finishes 50 minutes 50 minutes later so if you started four he's going to if you had 50 minutes to four that's going to put us at 450 so where is 450 on this number line so let's see so or in this timeline I guess I could say so let's see this is 415 so each of these marks must be 5 minutes this is 405 for 10 for 15 for 24 25 for 34 35 for 44 45 and then for 50 would be right over here so which of these choices has a dot at 450 this last choice has a dot has the red dot at 450 notice this is 50 minutes after he started at 4 o'clock let's do a few more of these Emira starts raking leaves at 2:30 p.m. and she finishes 25 minutes later which number line below has a red dark a red dot marking when Amira finishes raking the leaves so she starts at 2:30 and she finishes 25 minutes later so it looks like on this one each of these each of these spaces is 5 minutes so this is 2:30 so 2:30 so this is 5 10 15 20 25 minutes later and this place right over here is 255 and it looks like this first choice is actually the choice we're looking for they put the red dot 25 minutes after 2:30 notice this is 2 35 minutes after 2:30 ten minutes after 2:30 15 minutes after 2:30 20 minutes after 2:30 25 minutes after 2:30 let's keep going this is actually a lot of fun so the number line shows when scarlet starts and finishes Art Club alright that's when she starts that's when she finishes what time did scarlet start art club well let's see this is halfway between 3 o'clock and 3:30 so that's going to be 3:15 each of these marks go up by 15 minutes so this is at 3:15 what time did Scarlett finish art club so this is right in between 4:30 and 5:00 o'clock or you could say it's 15 minutes more than a 4:30 so that's going to be 4:45 4:45 how long will Scarlett in art club so let's think about it there's a couple of ways you could do it you could look at the line let's see so this to go from this point to this point that's 15 minutes then in 30 then 45 then 1 hour 1 hour 15 minutes 1 hour 30 minutes so you could say 1 hour 30 minutes or actually they want it all in minutes so 1 hour is 60 minutes plus 30 minutes is 90 minutes so actually let me just do it all in minutes again so this is as I move my mouse this is I'm going to talk about how many minutes I'm adding relative to this or from the start so 15 minutes gets us to 30 30 30 minutes 45 minutes 60 minutes 75 minutes 90 minutes so that's 90 minutes right over there another way to think about it is it would take 45 minutes to go from 3:15 to 4:00 o'clock 45 minutes to go from 3:15 to 4:00 o'clock that makes sense and then another 45 minutes to go from 4 o'clock to 4:45 so 45 plus 45 is going to be 90 minutes let's do let's do a couple of these so the number line shows when Anna starts and finishes reading a chapter in her book what time did Anna start reading so it says right over there she started reading at 8:10 p.m. 8:10 p.m. what time did Anna finish reading let's see let me make sure I'm reading so this is 820 this is 825 and they have one two three four five marks so each of these go up a minute so you could say it's a minute before 825 or four minutes after a 24 a twenty-one a 22 a 23 8 24 8 24 how long did Anna Reed well she starts shooting at 8:10 and finishes reading at 824 to go from 10 to 24 that means she read for 14 minutes and you could even count it over here 1 2 3 4 5 6 7 8 9 10 11 12 13 14 let's do one more Muhammad speaks on the phone for 15 minutes and finishes his phone call at 9:20 a.m. which number line below has a green dot marking when Mohammad starts his phone call alright it finishes at 9:20 so it finishes let's see where's 9:20 on this number line so it looks like each of these marks go up by 5 minutes so this is 9:15 and I was able to figure that out because we have three marks that go to 9:15 from 9:00 to 9:15 so this is 905 9:10 9:15 said this would be 9:20 so this is when he finishes 9:20 and he was on the phone for 15 minutes so and remember we don't want to mark when he finished they tell us that it's 9:20 we want to mark when he started so if he's on the phone call for 15 minutes and he finishes at 9:20 he's going to finish 15 minutes or sorry if he's on the phone for 15 minutes and he finishes at 9:20 he's going to start 15 minutes before 9:20 so 5 10 15 he's gonna start at 905 so that's this choice right over here another way you could think about is look if I'm at 9:20 and I go 15 minutes before 9:00 20 20 minus 15 is 5 so that's going to get me to 905 and we could just make sure we feel good about it if he starts his phone call at 59 oh five and he speaks for 15 minutes 5 10 15 he's going to finish his phone call right over here at 9:20 which is exact be what they described