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Age word problem: Arman & Diya

Sal solves the following age word problem: Arman is 18. Diya is 2. How many years will it take for Arman to be 3 times as old as Diya? Created by Sal Khan.

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  • blobby green style avatar for user Lizzie Whittington
    I understand the video, but I have trouble answering the problems on my own. I don't understand which one you are supposed to times and how you are supposed to tell. For example: Daniel is 40 years older than Vanessa. 12 years ago, Daniel was 3 times older than Vanessa.
    Which part of the equation do you times? I thought it was Vanessa's part (the smaller one) to make it the same amount as Daniel's but I keep making errors and am not getting anywhere.
    I know the example I have made does not make any sense, but if you could just show the process and how to put each part into the equation, I'd be grateful as I'm getting very frustrated!
    (1 vote)
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    • sneak peak green style avatar for user Hao
      Don't worry! There's always something you don't know!
      It takes patience and courage! One day you will master it!

      @Lizzie Whittington, I can't answer your question because there is no question. But I can tell you something. Sometimes you have to think out of the box and answer the question, sometimes you don't fully understand the question, then you read the question again, again and again until you understand it. Which part of the equation do you times? Well sometimes it involves you reading in on perspective or another. Once you fully understand it, you can translate it into algebraic language.

      You just need to understand what the question is saying
      (2 votes)
  • orange juice squid orange style avatar for user Elli Ferrara
    I literally am so confused. I have no idea how to do this and I don't even know what I don't know. Help please!
    (3 votes)
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  • blobby green style avatar for user James Milo
    So I solved it a little differently. I used A as the age of Arman and D as the age for Diya.

    A - D = 16
    A = 3D

    Solving for D we get 8 and we can verify that A = 3(8) = 24 is correct.

    We then know if Diya is 2, the difference is 6 years.

    Is this a valid way to solve this or did it just happen to work out that way.
    (4 votes)
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  • blobby green style avatar for user Wajid Hussain
    mary age is 2/3 that of peter,s .two years ago mary,s age was 1/2 of what peter,s age will be in 5 years time .how old is peter now?
    (2 votes)
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    • blobby green style avatar for user rolliver
      Instead of riding a tricycle, Nilda walks from her house to school after she learned that walking is good for health. If the time in walking the distance from the house to school is 4kph is 30 min longer than what is required at 5kph when taking the tricycle. Find the distance.
      (2 votes)
  • leafers tree style avatar for user Eli Sutton
    Helpful as this video is, I still am tying to figure out this problem.

    Ben is 4 times as old as Ishaan and is also 6 years older than Ishaan.
    How old is Ishaan?

    Can someone please help me with this problem, thanks!
    (3 votes)
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    • stelly blue style avatar for user Kim Seidel
      Let B = Ben's age and I = Ishaan's age.
      Translate the sentence.
      The 1st part gives you: B = 4I
      The 2nd part gives you: B=6+I
      Since B is equal to both, you can set them equal to each other and solve for I
      4I = 6+i

      Hope this helps to get you started.
      (1 vote)
  • mr pants teal style avatar for user Omniscient
    At the bottom it says "Imran is 18. Diya is 2. How many years will it take for Imran to be 3 times as old as Diya?" Shouldn't Imran be Arman?
    (2 votes)
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  • old spice man green style avatar for user minihardison001
    I know how to do the math really well, but when it comes to word problems I get stuck and don't know what to do. Is there a specific method or any techniques I can do to set an equation or a word problem up?
    (1 vote)
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    • blobby green style avatar for user Zach Higgins
      To me, and this is just my opinion, how I look at it, the difficulty of word problems means it's very healthy to do word problems.

      In traditional math in most cases we're given the logic beforehand, and we just have to learn the formulas and follow the rules -- do the mindless grunt work, but none of the logic.

      With word problems, you have to construct the logic yourself, which is much more difficult for most people (we're not as purely rational as we credit ourselves, but it can be learned -- and word problems are a good place to start).
      (2 votes)
  • leaf red style avatar for user TheAttack
    I cannot understand one of the practice questions:
    "Micheal is 12 years older than Brandon. Seventeen years ago, he was 4 times as old as Brandon."

    So I first did m=b+12, representing Micheal's Age. Then I wrote the equation m-17=4b, representing how 4 times Brandon's age was equal to Micheal's age 17 years ago. So, I plugged my m into the 2nd equation, and got this:

    b+12-17=4b
    -5=3b
    b=-5/3

    Obviously that's wrong, but I don't understand how I could have constructed the equation incorrectly.
    (2 votes)
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  • blobby green style avatar for user jj79052
    magret's age is a half of given's.four years ago magreth age was one third of given's what will be given's in 4 years
    (1 vote)
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    • mr pink red style avatar for user andrewp18
      m = margret's age
      g = givens age
      m = g/2
      m - 4 = g/3
      Solve for g + 4
      We can solve the system for g fairly quickly using the method of elimination:
      4 = g/2 - g/3
      4 = 3g/6 - 2g/6
      4 = g/6
      g = 24
      Given is 24 years old. So in four years he should be:
      g + 4 = 24 + 4 = 28
      (2 votes)
  • hopper jumping style avatar for user yoav mantine
    how do you solve age problems that are different(in the way you work out the answer)?
    (1 vote)
    Default Khan Academy avatar avatar for user

Video transcript

Let's say that Arman today is 18 years old. And let's say that Diya today is 2 years old. And what I am curious about in this video is how many years will it take-- and let me write this down-- how many years will it take for Arman to be three times as old as Diya? So that's the question right there, and I encourage you to try to take a shot at this yourself. So let's think about this a little bit. We're asking how many years will it take. That's what we don't know. That's what we're curious about. How many years will it take for Arman to be three times as old as Diya? So let's set some variable-- let's say, y for years. Let's say y is equal to years it will take. So given that, can we now set up an equation, given this information, to figure out how many years it will take for Arman to be three times as old as Diya? Well, let's think about how old Arman will be in y years. How old will he be? Let me write here. In y years, Arman is going to be how old? Arman is going to be-- well, he's 18 right now-- and in y years, he's going to be y years older. So in y years, Arman is going to be 18 plus y. And what about Diya? How old will she be in y years? Well, she's 2 now, and in y years, she will just be 2 plus y. So what we're curious about, now that we know this, is how many years will it take for this quantity, for this expression, to be three times this quantity? So we're really curious. We want to solve for y such that 18 plus y is going to be equal to 3 times 2 plus y. Notice, this is Arman in y years. This is Diya in y years. And we're saying that what Arman's going to be in y years is three times what Diya is going to be in y years. So we've set up our equation. Now we can just solve it. So let's take this step by step. So the left hand side-- and maybe I'll do this in a new color, just so I don't have to keep switching-- so on the left hand side, I still have 18 plus y. And on the right hand side, I can distribute this 3. So 3 times 2 is 6. 3 times y is 3y. 6 plus 3y. And then it's always nice to get all of our constants on one side of the equation, all of our variables on the other side of the equation. So we have a 3y over here. We have more y's on the right hand side than the left hand side. So let's get rid of the y's on the left hand side. You could do it either way, but you'd end up with negative numbers. So let's subtract a y from each side. And we are left with, on the left hand side, 18. And on the right hand side you have 6 plus 3 y's. Take away one of those y's. You're going to be left with 2 y's. Now we can get rid of the constant term here. So we will subtract 6 from both sides. 18 minus 6 is 12. The whole reason why we subtracted 6 from the right was to get rid of this, 6 minus 6 is 0, so you have 12 is equal to 2y. Two times the number of years it will take is 12, and you could probably solve this in your head. But if we just want a one-coefficient year, we would divide by 2 on the right. Whatever we do to one side of an equation, we have to do it on the other side. Otherwise, the equation will not still be an equation. So we're left with y is equal to 6, or y is equal to 6. So going back to the question, how many years will it take for Arman to be three times as old as Diya? Well, it's going to take six years. Now, I want you to verify this. Think about it. Is this actually true? Well, in six years, how old is Arman going to be? He's going to be 18 plus 6. We now know that this thing is 6. So in six years, Arman is going to be 18 plus 6, which is 24 years old. How old is Diya going to be? Well, she's going to be 2 plus 6, which is 8 years old. And lo and behold, 24 is, indeed, three times as old as 8. In 6 years-- Arman is 24, Diya is 8-- Arman is three times as old as Diya, and we are done.