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## 5th grade foundations (Eureka Math/EngageNY)

### Course: 5th grade foundations (Eureka Math/EngageNY) >Unit 6

Lesson 2: Topic B & D: Foundations

# Math patterns: toothpicks

Sal explores a pattern of creating figures with toothpicks. Created by Sal Khan.

## Want to join the conversation?

• For the toothpick video.

He does 6+5(x-1) x= # of houses

Can you do...

x5+1

I think Sal did the other way as a representation of the toothpicks but both ways would work. Please answer. :)
• YES!You are right x5+1 does the same thing as 6+5(x-1) x= # of houses GOOD CATCH.
• Don't you just love khan acedemy
• well kinda but mostly no
• why is he using toothpicks for his town house
• Because he's just making an art piece. (Or he's too poor to buy wood, nails, cement, and the other building supplies.)
• I'm just wondering why he complicated the calculation. I tried calculating myself for 500 houses before him solving the problem and did it this way
500*5+1=2501. He gets the same but in a much complicated matter. Is there something else I'm missing here? Some other type of lesson?
• He was probably trying to make it more clear that the first house requires 6 sticks, the parenthesis are there to subtract the multiplier before multiplying it to the multiplicand.
• you can also do this formula for any number of given toothpicks as long as they share 2 toothpicks in common :

((number of houses * (number of toothpicks need)) - (number of houses -1) = number of toothpicks need
• do I learn?
• I do not get it...Can someone say which grade this is and also how I can understand?
• why couldn't you just multiply number of houses times 5 +1 as in (6*5)+1=
• Yes, you could use 5n+1 where "n" is the number of houses.
• What is divisor
• A dividend is the number to be divided, and a divisor is the number you divide by. A divisor is also a number that divides a number without leaving a remainder.

Example:

(1.) 20/4 (20 is the dividend. 4 is the divisor.)
(2.) 20/4 = 5 (4 is a divisor of twenty because it goes into twenty five times without leaving a remainder.)
• Why would they say "add (let's say) 5 and then subtract one", what's the point of saying subtract one when you could've just said "add 4"? Plus, it would make the questions more understandable.