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soo i'm having trouble interpreting this question: 

 

"Melissa is four times as old as Dan. Twenty years from now, Melissa will be twice as old as Dan then. What is Melissa's present age?"

 

suppose m is melissa, and d is dan

 

i get that m = 4d, and d remains as is.

 

in the second sentence, what does "Dan then" even mean here? does that mean that we won't be adding 20 there?

 

any help appreciated, thanks.

Guest Sep 19, 2018

Best Answer 

 #1
avatar+13044 
+2

M=4D   presently

in 20 years:

 

M+20 = 2(D+20)

M+20 = 2D +40

M = 2D + 20            From the first equation    1/2M = 2D    Substitute this

M=1/2M + 20

1/2M = 20

M= 40        D=10    

And in 20 years

M= 60        D=30

ElectricPavlov  Sep 19, 2018
 #1
avatar+13044 
+2
Best Answer

M=4D   presently

in 20 years:

 

M+20 = 2(D+20)

M+20 = 2D +40

M = 2D + 20            From the first equation    1/2M = 2D    Substitute this

M=1/2M + 20

1/2M = 20

M= 40        D=10    

And in 20 years

M= 60        D=30

ElectricPavlov  Sep 19, 2018
 #2
avatar
+1

wow, thank you

how did you get the 1/2m = 2d?

Guest Sep 20, 2018
 #3
avatar+93667 
0

Hi, I like it when people ask for more explanation.   

 

The very first line is   M=4D

 

If I divide both sides by 2 then I get.

 

\(\frac{1}{2}M=2D\)

Melody  Sep 20, 2018

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