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05-21-2011, 06:49 AM
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19,562 posts, read 20,839,092 times
Reputation: 7065
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2
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05-21-2011, 07:59 AM
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Location: Victoria TX
33,145 posts, read 23,680,937 times
Reputation: 21657
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OK, then, express this algebraically:
You want to add 9+3, and multiply that by 2, and then divide 48 by that product. You will get 2. How do you express what you just did?
48÷2(9+3) is the only way.
You get 288 is by dividing 48 by 2, and then multiplying that by the sum of 9 and 3. How do you express that?
(48÷2)(9+3) = 288. Not the same.
The correct answer is 2. Now I remember why I loved algebra. It taught me to think, which turned out in later life to be very useful.
Last edited by jtur88; 05-21-2011 at 08:12 AM..
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05-21-2011, 10:31 AM
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Location: Brooklyn, New York
1,153 posts, read 795,925 times
Reputation: 734
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Quote:
Originally Posted by jtur88
OK, then, express this algebraically:
You want to add 9+3, and multiply that by 2, and then divide 48 by that product. You will get 2. How do you express what you just did?
48÷2(9+3) is the only way.
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LMAO what??? If you want to get 2, the correct expression is 48÷(2(9+3)).
Quote:
You get 288 is by dividing 48 by 2, and then multiplying that by the sum of 9 and 3. How do you express that?
(48÷2)(9+3) = 288. Not the same.
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The correct expression for 288 is 48÷2(9+3), because you go from left to right after parenthesis.
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The correct answer is 2. Now I remember why I loved algebra. It taught me to think, which turned out in later life to be very useful.
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Your algebra fails. |
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05-21-2011, 11:12 AM
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Location: Las Flores, Orange County, CA
25,896 posts, read 40,983,045 times
Reputation: 14804
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Quote:
Originally Posted by jtur88
OK, then, express this algebraically:
You want to add 9+3, and multiply that by 2, and then divide 48 by that product. You will get 2. How do you express what you just did?
48÷2(9+3) is the only way.
You get 288 is by dividing 48 by 2, and then multiplying that by the sum of 9 and 3. How do you express that?
(48÷2)(9+3) = 288. Not the same.
The correct answer is 2. Now I remember why I loved algebra. It taught me to think, which turned out in later life to be very useful.
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Are you sure? |
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05-21-2011, 11:32 AM
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Location: Somewhere in northern Alabama
9,385 posts, read 16,731,472 times
Reputation: 10260
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It boils down to weak syntax and using an inferred operator. Those who take the inferred operator as having to hold to the left to right processing order will get one answer, those who tend to group before doing a left to right order will get the other. It doesn't happen as much in math as in everyday language. I always get a kick out of the signs and advertising that tout "Big Baby Sale." If you don't buy in to the convention that there is an unsaid word, you go looking for babies to buy.
Although the 288 version is technically correct, it is sloppy.
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05-21-2011, 11:40 AM
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Location: Chicago
2,906 posts, read 2,049,630 times
Reputation: 1625
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48÷2(9+3)
48÷2(12)
48÷24
2
What's so hard about that?
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05-21-2011, 11:56 AM
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7,922 posts, read 4,002,096 times
Reputation: 5892
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Quote:
Originally Posted by Alacran
48÷2(9+3)
48÷2(12)
48÷24
2
What's so hard about that?
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It's wrong because after you do the parentheses (9+3), you work left to right. The expression would be better if you added the parentheses, but in algebra they are not necessary.
48÷2(9+3)
48÷2(12)
24(12)
288
If you want 2 the correct expression would be
48÷(2(9+3))
The Language of Algebra - Order of operations - First Glance
Quote:
When expressions have more than one operation, we have to follow rules for the order of operations:
First do all operations that lie inside parentheses.
Next, do any work with exponents or radicals.
Working from left to right, do all multiplication and division.
Finally, working from left to right, do all addition and subtraction.
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05-21-2011, 11:58 AM
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Location: Brooklyn, New York
1,153 posts, read 795,925 times
Reputation: 734
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Quote:
Originally Posted by Alacran
48÷2(9+3)
48÷2(12)
48÷24
2
What's so hard about that?
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After you get to 48÷2(12) you have to do 48÷2 first, because division comes before multiplication in this case.
48÷2(9+3)
48÷2(12)
24(12)
288
You'd get 2 only if you had 48÷(2(9+3)) - in math if you want to express division as a denominator you have to use extra parenthesis.
48÷(2(9+3))
48÷(2*12)
48÷24
2 |
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05-21-2011, 01:31 PM
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Location: Las Flores, Orange County, CA
25,896 posts, read 40,983,045 times
Reputation: 14804
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Quote:
Originally Posted by Alacran
48÷2(9+3)
48÷2(12)
48÷24
2
What's so hard about that?
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2 + 2 = 5; What's so hard about that? |
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05-21-2011, 02:01 PM
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14,418 posts, read 7,248,499 times
Reputation: 6044
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Quote:
Originally Posted by jtur88
OK, then, express this algebraically:
You want to add 9+3, and multiply that by 2, and then divide 48 by that product. You will get 2. How do you express what you just did?
48÷2(9+3) is the only way.
You get 288 is by dividing 48 by 2, and then multiplying that by the sum of 9 and 3. How do you express that?
(48÷2)(9+3) = 288. Not the same.
The correct answer is 2. Now I remember why I loved algebra. It taught me to think, which turned out in later life to be very useful.
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Wow. You just lost all credibility on this board. |
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