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Subtraction word problem: tennis balls

Sal solves a 2-step subtraction word problem with numbers less than 100.

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  • blobby green style avatar for user Bree Newsom
    Can you just add than subtract
    (8 votes)
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  • marcimus pink style avatar for user Varija Mehta
    How can I tell if I am adding or subtracting?
    (0 votes)
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    • starky ultimate style avatar for user Connor A.
      I think of it as money like this guy above me, when you put money in a bank, you are checking in, and when you are pulling money out your are withdrawling or taking a way.

      example:
      Jill has 100,000,000 dollars in her bank, and she adds 10,000,000, then she takes 5,675,000 away. how much does she have left?

      HOPE IT HELPS!
      (1 vote)
  • marcimus purple style avatar for user zozo7
    do you always start with the bigger number
    (2 votes)
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    • piceratops ultimate style avatar for user Hecretary Bird
      For now, the bigger number will always be the number that you subtract the smaller number from. Big - Small = Positive Difference. Later, you'll get introduced to what happens when you subtract a larger number from a smaller number, which leads you to a whole different class of numbers that are less than 0.
      (3 votes)
  • aqualine tree style avatar for user aimee valenzuela
    How do you subtract a smaller number to a bigger number?
    (1 vote)
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  • blobby green style avatar for user allison.1478
    Is there a easyer way to math?? Because I'm not very good at math.
    (1 vote)
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    • mr pants green style avatar for user Una W.
      allison.1473: Don't ever say you are not good at math! Math is about so much more then just solving equations, it's about seeing numbers in the world around you. As Bug Sanders said, it will take practice. But as you do more and more math you will find ways to do math that are easier for you. For now, just try to practice a lot, be open to new ideas and techniques, and keep on asking questions!
      (3 votes)
  • duskpin sapling style avatar for user 여름
    Hi. Can someone help me with a question?
    (3 votes)
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  • duskpin sapling style avatar for user 여름
    I have problems when it comes to word problems. Can someone help me with this problem? This is the problem: Your class is holding a fundraiser for a local charity. After the first week, your class raised 1/8 of your goal. After the second week, your class raised a total of 3/5 of your goal. What fraction of the goal was raised during the second week of the fundraiser?
    All answers are highly welcome. Thank you^^
    (1 vote)
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    • aqualine ultimate style avatar for user Asher Naval
      I think I'm too late to answer this but I'll still show you the answer.
      First you have to identify the given, which are the goal (1), the first week progress (1/8), and the total goal after the second week (3/5). Since the class finished 1/8 of the goal after the first week, and you know how many did the class raised after the second week (3/5), the equation to find the number is 1/8 + ? = 3/5 or 3/5 - 1/8 = ?. To find the answer, you need to find the LCD, which is 40, so that makes it 24/40 - 5/40 = ?. Subtract the nominators and the answer is 19/40.
      (2 votes)
  • blobby green style avatar for user joshharr1339
    it's just regular subtracting why is tennis balls important they don't add anything except to the story and why does a teacher have tennis balls?
    (1 vote)
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  • aqualine ultimate style avatar for user Cozy
    He is okay at this stuff! But yet I never learn
    (1 vote)
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  • blobby green style avatar for user Jennifer Henderson
    why can't you just do the unit test
    (1 vote)
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Video transcript

- Mrs. Grange's second grade class has 45 tennis balls. Whenever I do a word problem like this I just like to write down the information that they're giving me. So we're gonna start with 45 tennis balls. They then tell us that 19 tennis balls, so she starts with 45 tennis balls to play with at recess. They then tell us that 19 tennis balls get thrown over the fence and 6 tennis balls just disappear. How many tennis balls does Mrs. Grange's class have left? So what I'd like to do, when I do these type of word problems, let's say, okay, first of all where am I starting from? Well, I'm starting from 45 tennis balls and then whats happening? Am I gaining tennis balls or am I losing tennis balls? Well I started with 45 or Mrs. Grange's class started with 45 then 19 tennis balls get thrown over the fence so they're losing the balls. And then another 6 tennis balls disappear, so both of these are losing tennis balls. And since I'm losing something, since I'm losing the tennis balls, or some of the tennis balls that I started with I should subtract here. Another clue that subtraction might be interesting is because it says how many tennis balls does Mrs. Grange's class have left, which implies that, well, she doesn't have all the tennis balls that she started with so we're probably going to subtract some balls. But it comes straight out of the word problem. 19 tennis balls get thrown over the fence, she loses them, so we should subtract that from the original amount. And then another 6 just disappear, so we should then subtract that on top of the 19, so let's do that. So let's first subtract the 19. So we start with 45 tennis balls, and then 19 balls get thrown over the fence, so 19 get thrown over the fence so we're subtracting them. They lose those balls, so what is this going to be? Well if we look in the ones place we have 5 ones minus 9 ones. Well, since 5 is less than 9 we want to do some regrouping. So let's go to the tens place. Instead of 4 tens, lets try that as 3 tens, and then take that 10 , turn it into ones so it's gonna be 10 ones. 10 ones plus 5 ones is 15. Now we're ready to subtract. 15 minus 9, well that's gonna be 6 because 9 plus 6 is 15. And then 3 tens minus 1 ten is going to be 2 tens, so 26. But are we done? No. This is just the number of balls we have left after the 19 get thrown over the fence but before we count the 6 that just disappeared. So we also have to take away 6 for the 6 balls that disappeared. So let's do that. So after 19, so we started with 45, 19 get thrown over the fence, we have 26 at that point. Then, 6 balls just disappear so we have, once again they disappear, they're not, you know, magically appearing. Since they're disappearing we subtract. So we, they're disappearing, so we want to subtract those. So how many do we have left? Well, 6 ones minus 6 ones is 0 ones. 2 tens minus, well nothing here, that's just going to be 2 tens. So how many do we have left? Well, or how many does Mrs. Grange's second grade class have left? Well you see it right here. They have 20 tennis balls, 20 tennis balls left. Started with 45, 19 get thrown over the fence so they lose them, that's why we subtracted. That gets us to 26, then 6 of them disappear so we take the 6 away from the 26 to get to 20.