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Timothy is 8 years older then his sister, in 5 years from now she will be half Timothy's age. How old is timothy and his sister now?
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This problem can be solved in several ways.
I will show you two different ways to solve.
1. Two unknowns and two equations
Let x be the Timothy's age, an let y be the sister's age.
Then from the condition, you have these two equations
x = y + 8 (1)
x+5 = 2*(y+5) (2)
Substitute into equation (2) this expression for x of equation (1). You will get
y + 8 = 2*(y+5)
Simplify and find y
y + 8 + 5 = 2y + 10
8 + 5 - 10 = 2y - y
3 = y.
Thus the sister's age is 3 years.
From equation (1), then x = 3 + 8 = 11 is the Tymothy's age.
ANSWER. Tymothy is 11 years old; the sister is 3 years old.
2. Mental solution in your head without using equations
In 5 years, two events will happen simultaneously:
Timothy will be 8 yeras older and two times as old as the sister.
Hence, they will be 8 and 16 years old then.
It means that now they are 8-5 = 3 and 16-5 = 11 years old.
You get the same answer
Solved two times to provide your better understanding.
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There is a bunch of lessons on age word problems
- Age problems and their solutions
- HOW TO algebreze and to solve age problems?
- A fresh formulation of a traditional age problem
- Really intricate age word problems
- Selected age word problems from the archive
- Age problems for mental solution
- Age problem for three participants
- Miscellaneous age problems
in this site.
Read them and become an expert in solving age problems.
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this online textbook under the topic "Age word problems".
Save the link to this online textbook together with its description
Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson
to your archive and use it when it is needed.