WHAT IS THE FORMULA FOR SOLVING THIS QUESTION??????

notsure

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Feb 12, 2006
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How do you find the formula to solve this equation???? Its easy enough to figure out the answer but i need to know the formula!!!!!! A man is currently 1/2 of his brothers age in 15 yrs he will be 2/3 of his brothers age. what are their current ages???
 
Let m be the current age of the man.
Let b be the current age of the brother.

Then \(\displaystyle \L m = b/2\)
and \(\displaystyle \L m + 15 = \frac23(b+15).\)

Now solve for m and b.
 
Matt said:
Let m be the current age of the man.
Let b be the current age of the brother.

Then \(\displaystyle \L m = b/2\)
and \(\displaystyle \L m + 15 = \frac23(b+15).\)

Now solve for m and b.

THANKS MATE I ACTUALLY HAVE THAT WRITTEN DOWN BUT HOW DO I GET THE VALUES???
 
if you :

1) substitute b/2 for m in the 2nd equation


m+15=2/3(b+15)>>>>>>(b/2)+15=2/3(b+15)


2) distribute


b/2 + 15 = 2/3(b+15)>>>>>>b/2 + 15 = 2/3b + 10


3) simplify

b/2+15=2/3b+10
***-10******-10
_______________
b/2+5=2/3b


4) i hate working with fractions, distribute the denominator.

b/2+5=2/3b>>>>>6(b/2+5=2/3b)>>>>>>3b+30=4b


5) simplify again

3b+30=4b
-3b***-3b
________
30=b


6) now that you have found the value for b, substitute again

m=b/2>>>>m=30/2>>>m=15


7) HINT: you can always double check the solution by SUBSTITUTING.

m=15
b=30

m+15=2/3(b+15)
(15)+15=2/3(30+15)
15+15=2/3(45)
15+15=30

looks good to me :D
 
m = b / 2 [1]
m + 15 = 2(b + 15) / 3 [2]

Hate fractions too! So get rid of them right away:
(plus, unlike zerodegrees, I hate typing :wink: )
[1] * 2 : b = 2m [1]
[2] * 3 : 3m + 45 = 2b + 30 ; 2b = 3m + 15 [2]

Substitute [1] in [2]:
2(2m) = 3m + 15
4m - 3m = 15
m = 15

See how easy it is :shock:
 
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