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Current time:0:00Total duration:2:34

CCSS.Math:

my book is 58 pages I have already read 13 pages I plan to read five pages each day until I finished the book which equation could I use to find out how many days D it will take to finish reading the book so pause this video and see if you can figure that out okay so let's first think about the important information they're giving us they're giving us the number of pages that are in the book they're giving us how much we've already read we've already read 13 pages and they also tell us how much we plan to read I plan to read 5 pages each day until the book is finished and then we want an equation that it could use to find how many days and D is how we're going to represent the number of days let me do that in the same color it'll take to finish reading the book all right so if we knew how many pages we have to read and we were divided by the fact that I were reading 5 pages per day well then that would give us the number of days so how many pages do we have left to read in the book well the book is 58 pages we've already read 13 so we could subtract out 13 of those so this expression right over here this is how many pages we have left in the book we write that down how many how many pages left and if we want to figure out how many days it's going to take to read these we would divide this by how many pages we read each day and we see that we read five pages each day so if we divide this by five then this whole expression let me do it in this color this whole expression is going to tell us how many days left many days left and so this is going to be equal to D because D is the number of days left to finish reading the book now if we look at these choices that's exactly what we have right over here in choice C we can make sure that these others don't make sense 58 + 13 no that would be a situation where we're reading 13 pages more than number of pages that are in the book that doesn't make sense and that's happening for most choice a and choice B it would also not make sense to multiply by five because it's not going to take you five times more than the number of pages to read the book you're going to divide by five you're reading five pages every day and we are done