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Source: — Problem Solving |
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by raider » Sat Mar 22, 2008 11:17 am
1. (5^x) - ( (5^x)/(5^3) ) = 124 (5^y)

2. ( (5^x)(5^3) - (5^x) ) / 5^3 = 124 (5^y)

3. (5^x) ( (5^3) - 1 ) = (124)(5^3)(5^y)

4. (5^x)(124) = (124)(5^3)(5^y)

5. 5^x = (5^y)(5^3)

6. X= Y + 3

7. Y = X - 3

8. Answer: C
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by rros0770 » Thu Mar 27, 2008 12:09 pm
Hi Raider,

lost you on Step 3 there a bit

In step 3 I see how you have taken the denominator (5^3) on the LHS and got it onto the RHS of the equation, but I'm not sure how you removed one of the (5^x) from the LHS of the equation and substituted it with a 1. Don't know why I'm hung up on this, I'm sure its an easy explanation.

Thanks for the help
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by xilef » Thu Mar 27, 2008 12:46 pm
1. (5^x) - ( (5^x)/(5^3) ) = 124 (5^y)

2. (5^x)(1 - 1/5^3) = 124 (5^y)

3. (5^x)(124/5^3) = (124)(5^y)

4. (5^x) /(5^3)= 5^y

5. 5^x-3 = 5^y

y=x-3
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A slightly simpler soln

by anshul265 » Thu Mar 27, 2008 3:34 pm
1. 5^x-5^(x-3)= (124)(5^y)
2. (5^(x-3))(5^3-1)=(5^3-1)(5^y)
3. 5^(x-3)=5^y
4. Thus, y=x-3
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by rros0770 » Thu Mar 27, 2008 4:33 pm
Good looks, got it now, thanks guys!
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vic

by resilient » Tue Apr 01, 2008 12:42 am
there are variables in the choices can we pick numbers for this?
Appetite for 700 and I scraped my plate!
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