Multiplying by 0Date: 03/09/2001 at 04:23:12 From: Bruce Griffis Subject: Multiplying by 0 This may be a stupid question, but why, when multiplying any number by 0, do you get 0? If I have a dollar in my hand and multiply it by 0, won't I still have a dollar? If not, then who took my dollar? Date: 03/09/2001 at 08:41:28 From: Doctor Rick Subject: Re: Multiplying by 0 Hi, Bruce. They say the only stupid question is the one that you don't ask. Even "stupid questions" can lead to interesting insights if they make us look at the obvious in a new way. I don't know if I'll do that, but it could happen! What does your illustration mean? If I have a dollar and multiply it by 2, I have $2. I could just as well ask where the second dollar came from, as you can ask where your dollar went. Let's fix your picture to make it clear where money is coming from. Let's say you're a barber and every customer tips you a dollar. At the end of the day, how much have you made in tips? Multiply a dollar by the number of customers you had. If you had 10 customers, you made $10. If you had 20 customers, you made $20. So, what about the day that your shop was closed because of a blizzard? By your reasoning, you'd still make a buck, even though you had zero customers. No, it's clear that you make $0: $1 times 0 customers is $0. - Doctor Rick, The Math Forum http://mathforum.com/dr.math/ Date: 03/09/2001 at 08:48:18 From: Doctor Peterson Subject: Re: Multiplying by 0 Hi, Bruce. Picture multiplication by a whole number as making that many piles, each containing the original amount. If I start with a dollar and multiply by 5, I make 5 piles with a dollar in each. If I multiply by zero instead, I have zero piles; and zero piles (no matter how much I claim "each of them" has) will contain zero dollars. You can also go in the other direction, multiplying zero by anything; this should give the same result. So start with 0 dollars, and make 57 piles, each containing zero dollars. Again, the total is zero. I'm wondering if you are confusing "multiplying by 0" with "adding zero times as much." If you have a dollar in your hand and multiply it by ONE, you will still have the same amount; multiplying by one doesn't change anything. Multiplying by 2 takes what you had, makes another copy of it, and gives you back twice what you started with. But multiplying by zero takes away what you had and gives you none of it back. - Doctor Peterson, The Math Forum http://mathforum.com/dr.math/ |
Search the Dr. Math Library: |
[Privacy Policy] [Terms of Use]
Ask Dr. Math^{TM}
© 1994-2013 The Math Forum
http://mathforum.org/dr.math/