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:3:01

CCSS.Math:

a theater has a total of 63 seats and a rectangular grid here they are right over here it currently has nine rows each was an equal number of seats we see that one two three four five six seven eight nine rows how many total seats will it have if it adds two seats per row so how many total seats will it have if it adds two seats per row so we want to figure out is a total number of seats so let's say that the total the total is going to be equal to the number of seats that the theater already has and they tell us that they have 63 seats in a rectangular grid so it's going to be 63 seats plus the new seats plus however many it adds so plus plus the new seats well what are the new seats going to be well the new seats are going to be I have nine rows and I'm adding two seats per row so the new seats are going to be nine rows times two seats per row so we could say that the total we could say that the total is going to be equal to 63 plus 63 plus nine times two and we'll talk more about order of operations but clearly in this situation we want to multiply nine times two to figure out the total new number of seats and then we want to add that to 63 and if we just write it like this multiplication takes you will always do multiplication and when you're just seated in a row like this you will do the multiplication before you do the addition so this is literally saying hey multiply 9 times 2 first then add to 63 which is exactly what we care about and what is 9 times 2 well let's add those two seats per row so that's 2 4 6 8 10 12 14 16 and 18 so 2 times 9 2 4 6 8 10 12 14 16 18 is 18 so we're adding 18 new seats so let me write this down I covered up my old total so total is equal to 63 63 plus 18 plus 18 I had 63 seats I'm now adding 18 seats so total my total number of seats is now going to be 63 plus 18 let's see 8 plus 3 is 11 60 plus 10 is 70 70 plus 11 is going to be I have 80 I have 81 seats I had now I have 9 rows which 9 seats each which gets me 81 total