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Calculating profit with addition and subtraction | 4th grade math (TX TEKS) | Khan Academy

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    - [Instructor] We're told
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    that Lily bought a backpack for $26.45
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    and spent $18.97 on
    accessories to decorate it.
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    She sold the decorated
    backpack for $67.56.
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    What was Lily's total profit
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    from selling the custom backpack?
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    All right, pause this
    video and have a go at that
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    before we do this together.
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    Okay, well let's just first
    think about what profit is.
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    So profit, you can view it as
    money earned, money earned,
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    minus money spent, minus money spent,
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    is going to be equal to your profit.
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    Let me do this another color.
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    So this is going to be
    equal to your profit.
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    So what you need to do is just figure out
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    what's the money earned
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    and then what's the money
    spent and then subtract them.
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    So what's the money earned?
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    How much did she bring in?
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    Well, the money earned in this situation
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    is going to be what she
    sold the backpack for.
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    That's what she got.
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    So the money earned is this
    piece right over here, $67.56.
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    That's the money earned.
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    So we have $67.56,
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    and then we're going to subtract
    from that the money spent.
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    Now what was the money spent?
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    Well, she spent some money twice.
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    She bought a backpack for $26.45
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    and then she spent another $18.97
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    on accessories to decorate it.
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    So the total money spent...
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    I'll do it over here.
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    Money spent, the total...
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    I mean, I'll just write it here.
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    Let me just write it.
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    So money spent, money
    spent, is equal to $26.45.
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    Actually, let me do it over here
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    'cause actually I just wanna line them up
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    so I can just do the computation.
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    So it's $26.45 plus $18.97.
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    Let's add these together.
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    We'll go to the pennies
    or the hundredths place.
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    Five plus seven is 12.
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    Go at the two there, regroup that one.
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    And now we have one plus four plus nine
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    is going to get us to 14.
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    We could put the four there.
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    Regroup that one. That's a whole.
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    Put the decimal there.
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    One plus six plus eight, that's seven.
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    Plus eight, which is 15.
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    Regroup the one.
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    One plus two plus one is 45
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    or it's 40 or four.
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    And so this is $45.42
    cents is what she spent.
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    So money earned, that's
    what she brought in,
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    minus what spent is $45.42.
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    And so now we just have
    to do this subtraction
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    to get our profit.
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    And actually let me do that over here.
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    So if I have 60...
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    That's too light of a color.
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    If I have $67.56
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    and from that I am subtracting $45.42.
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    So let's see if I have six minus...
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    I'll put the decimal here.
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    Six minus two is going to be four.
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    Five minus four is one.
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    Seven minus five is two.
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    Six minus four is two.
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    So we get to $22.14 of profit.
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    Let's do one more example here.
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    So let me delete this
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    and now let me bring up another problem.
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    And move it up so we can see it properly.
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    And so here we are told that Maya spent
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    $9.24 on ingredients to bake two cakes.
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    She sold one cake for $13.29
    and the other for $17.45.
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    What was the total profit
    from selling the two cakes?
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    Again, you could pause this
    video, have a go at that.
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    Well, once again, it's money earned
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    minus money spent.
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    So what's the money earned?
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    So the money earned here is...
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    So this is how much she spent and then,
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    but what she sold it for,
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    that's the money that she got.
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    So she sold one cake for 13.29
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    and the other for 17.45.
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    So let's see.
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    If we add the both of these.
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    That's her total money earned.
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    So nine plus five is 14.
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    One plus two plus four is seven.
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    Three plus seven is 10.
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    Regroup that one.
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    One plus one plus one is three.
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    So total money earned is $30.74
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    and from that we're going
    to subtract the money spent,
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    minus $9.24.
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    Let me do that in another color.
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    So minus $9.24, which is
    that right over there.
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    And we could do this separately,
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    or you might be able
    to do this in your head
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    because if you have 74
    cents minus 24 cents,
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    that's going to give you 50 cents.
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    And then $30 minus $9 is $21, is 21.50.
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    You could also write it out
    the way we did the last one
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    where you just put the
    9,24, line up the decimals
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    and subtract accordingly.
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    But that's her total profit
    from selling the two cakes.
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    And we're done.
Title:
Calculating profit with addition and subtraction | 4th grade math (TX TEKS) | Khan Academy
Description:

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Video Language:
English
Team:
Khan Academy
Duration:
05:05

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