Question 1151259: Liza is one year older than her sister. In four years Liza will be three times older than she is now. How old is Liza's sister now?
Found 3 solutions by josgarithmetic, ikleyn, MathTherapy:
Answer by josgarithmetic(39618)   (Show Source):
Answer by ikleyn(52790)  (Show Source):
You can put this solution on YOUR website! .
The original formulation in the post is DEFECTIVE, INACCURATE and potentially DANGEROUS.
The correct, accurate and safe formulation is THIS :
Liza is one year older than her sister. In four years Liza will be three times  as old as she is now.
How old is Liza's sister now?
Solution
Let x be the Lisa's age now.
Then from the condition
x + 4 = 3x. (In four years Liza will be three times as old as she is now).
From the equation,
4 = 3x - x
4 = 2x
x = 4/2 = 2.
So, Lisa is 2 years old now.
ANSWER. Lisa' sister is 2-1 = 1 year old now.
Solved.
-------------------
Here I want to explain you, why the original formulation in the post is DEFECTIVE, INACCURATE and potentially DANGEROUS.
In English, in distinction from many other languages, the statement
In four years Liza will be three times older than she is now.
means "In four years Liza will be FOUR times as old as she is now."
In English, it is the only possible interpretation --- and there is NO any other interpretation.
But it is, certainly and definitely, not that meaning the author of the problem was going to implement.
Probably, the author of the problem is/was not familiar with this norm/form of English --- so, learn it from my post.
The second message from me is that the "solution" and the setup in the post by @josgarithmetic is WRONG.
So, you better IGNORE his post for your safety.
Answer by MathTherapy(10552)  (Show Source):
|
|
|
