Age now and then | MathCelebrity Forum

Age now and then

D

Drew

New Member
I brute forced this and got a wrong answer, logic tells me is right. I tried the calculator here but maybe messed up the equation using another users problem as an example. Having no luck.

Problem:
Jacob is 4 times the age of Clinton. 8 years ago Jacob was 9 times the age of Clinton. How old are they now and how old were they 8 years ago?
 
Let j be Jacob's age and c be Clinton's age. We have:
  1. j = 4c
  2. j - 8 = 9(4c - 8)
Substitute (1) into (2)
(4c) - 8 = 36c - 72

Using our equation solver, we get c = 2
Which means j = 4(2) = 8

8 years ago, Jacob was just born. Which means Clinton wasn't even born yet.
 
Thank you, but I'm going to have to talk to my teacher about how someone can't be 9 times older than nothing....
 
she wrote it down wrong! The 9 should have been a 10.

So I tried 4c-8=40c-80 in the equation solver and it also came back with C=2 which was the same answer you got before?
 
she wrote it down wrong! The 9 should have been a 10.

So I tried 4c-8=40c-80 in the equation solver and it also came back with C=2 which was the same answer you got before?
Drew said:
she wrote it down wrong! The 9 should have been a 10.

So I tried 4c-8=40c-80 in the equation solver and it also came back with C=2 which was the same answer you got before?
Click to expand...
oh and my brute force answer was 12-48 and 8 years earlier was 4-40
 
I read it wrong before. Here you go:

Jacob is 4 times the age of Clinton. 8 years ago Jacob was 10 times the age of Clinton. How old are they now and how old were they 8 years ago?
  1. j = 4c
  2. j - 8 = 10(c - 8)
Substitute (1) into (2)
(4c) - 8 = 10c - 80

Equation solver gives us c = 12 which means j = 4(12) = 48.
8 years ago, j = 40 and c = 4 which holds the 10x rule.
 
math_celebrity said:
I read it wrong before. Here you go:

Jacob is 4 times the age of Clinton. 8 years ago Jacob was 10 times the age of Clinton. How old are they now and how old were they 8 years ago?
  1. j = 4c
  2. j - 8 = 10(c - 8)
Substitute (1) into (2)
(4c) - 8 = 10c - 80

Equation solver gives us c = 12 which means j = 4(12) = 48.
8 years ago, j = 40 and c = 4 which holds the 10x rule.
Click to expand...
Thank you, I see what I did wrong!
 
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