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

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

Lesson 3: Topic C: Foundations- Multiplying fractions and whole numbers visually
- Multiply fractions and whole numbers
- Compare with multiplication
- Compare with multiplication word problems
- Multiplication word problem: carrots
- Division word problem: row boat
- Multiplication and division word problems
- Multi-step unit conversion examples (U.S. Customary)
- US customary conversion word problems

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# Multiplication word problem: carrots

Created by Sal Khan.

## Want to join the conversation?

- At2:10Isn't it Same as finding
*Area*?

What if we had 1 carrot in 1st row 2 carrots in 2nd ................**n carrots in nth row**Then what is*Total number of carrots*? is there a*General Formula*?(30 votes)- The problem you described is this.. how much is 1 + 2 + 3 + 4 + 5 + ... + n and there is a formula that gives you the answer n*(n+1) / 2. The reason this is true is because you can always couple the smallest and largest numbers and get some constant (the constant is always n+1).. an example:

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8

1 + 8 = 9

2 + 7 = 9

3 + 6 = 9

4 + 5 = 9

So because you couple numbers you get n/2 pairs so to add all of them up we just have to multiply n/2 * constant = n/2 * (n+1) = n*(n+1)/2. I used an example where n is even, but it also works with odd n.(48 votes)

- I'M new here can someone please help me(4 votes)
- there are 1,760 yards in one mile. about how many miles will a runner have to run before seeing both a water station and trail maker at the same location? calculate the answer to the nearest hundredth of a mile.(2 votes)
- Why are you having us do that? That has nothing to do with anything. Why don't we work on the problem Sal gave to us.(2 votes)

- i need help doing multpication b(2 votes)
- what is 0 over 3 divided by 78965 plus o divided by 9876(2 votes)
- how do you compare with mutipcation.(2 votes)
- To be honest I think that is fall under area(2 votes)
- the product of 7 and a number is 4 more than 38. find the number(3 votes)
- At the zoo, there were 3 times as many monkeys as lions. Tom counted a total of 24 monkeys and lions. How many monkeys were there?(2 votes)
- can I keep doing math problems like division(1 vote)

## Video transcript

Toby is a farmer. He plants 12 rows of
carrots in a field. Each row has 6 carrots. How many carrots did Toby plant? So let's try to
visualize this thing. So they tell us each
row has 6 carrots. So let's try to visualize a row. So that's 1 carrot,
that's 2 carrots, that's 3 carrots, that's 4
carrots, that's 5 carrots, and that's 6 carrots. And I can even do,
just so it looks nice, the little leafy
part of the carrots. So we can visualize
these as carrots. So that's 1 row of carrots. They tell us each
row has 6 carrots. Now, there're 12 of these. He plants 12 rows of carrots. Let me see if I can
copy and paste this. So copy and paste. So that's 2 rows. I want to make sure
I have enough space. 2 rows. That's 3 rows. That's 4 rows. This is 5 rows. This is 6 rows. And actually, I can just copy
and paste the whole thing. This is 6 rows. I just need to double
that to get to 12 rows. So let me do that. So copy and paste. There you go. So there's 12 rows
right over here. And let's number this. So they tell us each row has
6 carrots-- 1, 2, 3, 4, 5, 6. They tell us he
plants a total of 12 rows-- 1, 2, 3, 4, 5,
6, 7, 8, 9, 10, 11, 12. How many carrots did Toby plant? Well, you could do
this exercise and then try to count all
of these carrots. But that seems a
little bit crazy. These are already
a lot of carrots. And especially if these
were even larger numbers, it would take you
forever to count it. Luckily for us, we have
multiplication as a tool that we can use. So if you have 12 rows and
each of those rows have 6, this is really 12 times 6. You're going to have 12 rows. In each of those,
you have 6 carrots. So you could say you
have 6 carrots 12 times. So it's going to be 12 times 6. If you remember your
multiplication tables up to 12, you'll remember that
12 times 6 is 72. So he has 72 carrots. Even if you only remember--
well, I'll just leave it there. If you remember your
multiplication-- which you should, because that
is one of the things in life that will have long-lasting
benefits-- it's 72 carrots.