Discover your age using a simple equation | Age Question Homework Statement"

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Homework Help Overview

The problem involves determining the current age of a person based on their relationship to their brother's age. The original poster states that they are currently half as old as their brother was seven years ago and that they are eleven years younger than their brother.

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss setting up equations based on the relationships described in the problem. There is an emphasis on defining variables for their ages and translating the conditions into mathematical expressions. Some participants express confusion over arriving at a negative age and question the correctness of their equations.

Discussion Status

Multiple participants are engaged in exploring different variable definitions and equations. Some have pointed out potential errors in the original setup, while others are attempting to clarify the relationships between the ages. There is no explicit consensus on the correct approach yet, but guidance has been offered regarding the equations.

Contextual Notes

Participants note the importance of correctly interpreting the relationships and conditions given in the problem statement. There is an acknowledgment of the potential for misunderstanding the age relationships, which may lead to incorrect conclusions.

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Homework Statement


Today i am half as old as my brother was 7 years ago. I am 11 years younger than my brother. How old am i?

2. The attempt at a solution
Let I = Me and B = Brother


Let: Brother age = x
Hence my age now = x -11

So, 7 years ago:
my brother was (x - 7)
and I was (x - 11 - 7)

Lets set an equation:
1/2 x I = B
This gives us 1/2 (x - 18) = x - 7
x - 18 = 2x - 14
x = -4

Why do I get a negative age? Can anyone help solve this one please?
 
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Natasha1 said:

Homework Statement


Today i am half as old as my brother was 7 years ago. I am 11 years younger than my brother. How old am i?

2. The attempt at a solution
Let I = Me and B = Brother


Let: Brother age = x
Hence my age now = x -11

So, 7 years ago:
my brother was (x - 7)
and I was (x - 11 - 7)

Lets set an equation:
1/2 x I = B
This gives us 1/2 (x - 18) = x - 7
x - 18 = 2x - 14
x = -4

Why do I get a negative age? Can anyone help solve this one please?

It helps to keep things straight (and make your work more readable) if you have two variables: b = brother's current age, m = my current age (both in years). The conditions are that (1) m = (1/2)(b-7); and (2) m = b-11. Try solving these two equations for m and b.
 
Natasha1 said:

Homework Statement


Today i am half as old as my brother was 7 years ago. I am 11 years younger than my brother. How old am i?

2. The attempt at a solution
Let I = Me and B = Brother


Let: Brother age = x
Hence my age now = x -11

So, 7 years ago:
my brother was (x - 7)
and I was (x - 11 - 7)

Lets set an equation:
1/2 x I = B
This gives us 1/2 (x - 18) = x - 7
x - 18 = 2x - 14
x = -4

Why do I get a negative age? Can anyone help solve this one please?
You have that your age now is (x − 18), which is right. (See corrections below)

That is (equal to) 1/2 of what your brother's age was 7 years ago: (x − 7)

Which thing should you take 1/2 of ?

Added in Edit: Thanks Chestermiller.
Corrections:
Today you are 11 years younger than your brother (is now)
What is that? Not (x − 18) .
 
Last edited:
SammyS said:
You have that your age now is (x − 18), which is right.

That is (equal to)1/2 of what your brother's age was 7 years ago: (x − 7)

Which thing should you take 1/2 of ?
Isn't his age now x-11? Isn't that half of what his brother was 7 years ago (x-7)?
 
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I will give a try but my variables choices will be different.
"Me", m
Brother, b

Today i am half as old as my brother was 7 years ago. I am 11 years younger than my brother. How old am i?

m=(1/2)(b-7)
AND
m=b-11

That system of equations is the exact translation of the description, using the variables as I've chosen.
Now, you solve that system, and you get what you get. If bad values result, then the description is at fault.
I have not tried to solve the equations yet.
 
Again continuing with the system
m=(1/2)(b-7)
AND
m=b-11

The second equation can give b=m+11.
Substitute into the first equation and solve for m, the number being asked for in the question.
m=4.
and then b=15.

The example problem is a good typical beginners' question.
 

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