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### Course: 4th grade > Unit 3

Lesson 1: Comparing with multiplication- Multiply by 1-digit numbers: FAQ
- Comparing with multiplication
- Comparing with multiplication and addition: giraffe
- Comparing with multiplication and addition: money
- Comparing with multiplication: magic
- Compare with multiplication
- Compare with multiplication word problems

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# Comparing with multiplication and addition: giraffe

Sal solves 2 multiplication comparison word problems. Created by Sal Khan.

## Want to join the conversation?

- why are the equations so hard?(13 votes)
- They are not hard, you just dont understand them so you need to get more practice on this.(24 votes)

- why do the equation look like that instead of it just being simple(7 votes)
- He is just making it easy(1 vote)

- The examples you used are easy but in khan, it is hard. Can you use the question khan? please(5 votes)
- I don't see the point of using a number line, you can do 2 + 2, 2 x 2, 1 + 1 + 1 + 1, etc. So why out of all ways you use a number line?(5 votes)
- so if i did kimmy is 20 feet tall and a horse is 3 times bigger than kimmy how tall would the horse be?.(3 votes)
- that is a good drawn giraffe(4 votes)
- but what if they want 70 divided by 40 what do we do(2 votes)
- One method is to reduce 70/40 to 7/4 (from dividing top and bottom by 10).

Then 7/4 = 1 3/4. Every 1/4 is 0.25, so 3/4 is 0.25 * 3 = 0.75. So the final answer is 1.75.

Another method is to do 40 into 70 using long division.

40 goes into 70 once with remainder 70-40 = 30.

Then 40 goes into 300 seven times with remainder 300-280 = 20.

Then 40 goes into 200 five times without a remainder.

So the answer is 1.75.

Have a blessed, wonderful day!(5 votes)

- Why is he explaining it in such complicated ways??(4 votes)
- cause he is very smart.

duh and who knows if i am 20.(1 vote)

- are giraffes really 18 ft tall(3 votes)
- yes they can be but sometimes it can be made up cuz they want you to learn.(4 votes)

- 3 times 6 = 18(3 votes)

## Video transcript

We're told that Imran is
two years older than Diya. Diya is 2. How old is Imran? So I encourage you
to pause this video and try to think
about this yourself. How old is Imran given
the information here? So let's use some letters to
represent Imran and Diya's age. Let's say that I is
equal to Imran's age. And let's say that D
is equal to Diya's age. So given that, what does
this first sentence tell us? It says that Imran's age, Imran
is two years older than Diya. So Imran's age is going to be
equal to Diya's age plus 2. That's what this first
sentence tells us. Imran's age is
Diya's age plus 2. Imran is two years
older than Diya. Another way you
could think about it, if we were to imagine
their ages on a number line right over here,
so if this is 0, and then this is Diya's
age right over here-- let me do it in that same color. This is Diya's age
right over here. If you were to add
2 to Diya's age, if you were to go
to more, so plus 2, you would get to Imran's age. So that's what this
first sentence tells us. Then they tell us
that Diya is 2. So that's like
saying that D, which we're using to represent
Diya's age, that's going to be equal to 2. So this thing is equal to 2. So we can rewrite
this as Imran's age is equal to Diya's age,
which we know to be 2 plus 2. So what's 2 plus 2? Well, you know that. That's going to be 4. So Imran's age is
going to be equal to 4. If this is 2 right
over here, and then you were to go up 2 more,
you're going to get to 4. Imran's age is 4. Let's try one more of these. So here we're told that the
giraffe at the zoo is 3 times taller than Shantanu. Shantanu is 6 feet tall. How tall is the giraffe? So once again, I encourage
you to pause this video and try to think
about it on your own. Well, let's do the same idea. Let's use some
letters to represent the different heights, so G
for giraffe and S for Shantanu. I'll use G for the
height of the giraffe. The height of the
giraffe is 3 times taller-- not 3 more
feet-- 3 times taller than Shantanu's height. So we could say that
the giraffe's height is equal to 3 times
Shantanu's height. So let's be clear. G represents the
height of the giraffe, S represents the
height of Shantanu. So another way of
thinking about it-- let me see if I can draw
a giraffe reasonably here. So if this is the
giraffe-- actually, this isn't a bad job
at drawing a giraffe. So this is the giraffe
right over here. They're saying that if you
take Shantanu's height times 3, you get to the giraffe's height. Actually, a giraffe might
have longer legs than that. So this is G. The height
of the giraffe is G. So let's say this is
Shantanu's height. If I multiply that by 3, I
get the giraffe's height. Let me see-- one, two. So Shantanu might look
something like this. And if you took 3
times his height, so this is 1 time his height,
2 times his height, 3 times his height, you would get to
the height of the giraffe. So that's what this
first sentence tells us. Shantanu is 6 feet tall. So they tell us that this height
right over here is 6 feet. Or another way of saying
it is S is equal to 6 feet. How tall is the giraffe? Well, once again, S
is equal to 6 feet. So the giraffe's height is equal
to 3 times Shantanu's height, which we now know to be 6
feet, so 3 times 6 feet. So in feet, the giraffe's
height is 3 times 6. Well, we know that
3 times 6 is 18. And we're dealing with feet. So the giraffe's
height is 18 feet. And you see that
right over here. 6 feet plus another 6
feet plus another 6 feet, or 6 feet times 3 is going
to get you to 18 feet.