Question 1002578: Question: Jake is 13 years old. In 3 years his grandpa will be twice as old as Jake's dad, and in 7 years his grandpa will be four times older than Jake. How old is Jake's dad?
I've tried 13*4=52. 52-7=45. 45+3=48. 48/2=24.
I'm not sure what steps I'm missing or what math I'm doing wrong
Found 3 solutions by josgarithmetic, mananth, ikleyn:
Answer by josgarithmetic(39791)   (Show Source):
You can put this solution on YOUR website! j, g, d, for Jake, Grandpa, Dad
Examining the description very carefully, you should be able to form this system of equations:
One of the variables is already given as known, so you can substitute for it now and you will have a system of two equations, just in the unknown variables, g and d.
 ---------Grandpa;
but still you want to know d, from the other equation in the last system;
 -----------Jake's dad.
Answer by mananth(16949)  (Show Source):
You can put this solution on YOUR website!
Jack is 13 now
After 7 years he will be 20
grandpa will be 4 time older than Jake
20 + 80 = 100
(three years from now means 4 years earlier )
4 years ago grandpa was 96
and at that time he was twice dad,s age
dad,s age = 48
dads age now is 48-3 = 45 years
Answer by ikleyn(53742)  (Show Source):
You can put this solution on YOUR website! .
Jake is 13 years old. In 3 years his grandpa will be twice as old as Jake's dad,
and in 7 years his grandpa will be four times older than Jake. How old is Jake's dad?
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As printed in the post, this problem is a lame horse with three legs.
Why ? - Because no one professional English writer will write "will be four times older than Jake".
Why ? - Because it is not accepted in English to formulate Math problems using this form.
So, I will interpret the whole problem in THIS way
Jake is 13 years old. In 3 years his grandpa will be twice as old as Jake's dad,
and in 7 years his grandpa will be four times as old as Jake. How old is Jake's dad?
In this form, the problem is a nice arithmetic problem to solve it MENTALLY by reasoning.
Jack is 13 years old now.
In 7 years, Jack will be 13+7 = 20 years old.
Hence, in 7 years, Jack's grandpa will be 20*4 = 80 years old.
It means that Jack's grandpa is 80-7 = 73 years old now.
In 3 years, the grandpa will be 73+3 = 76 years old.
Hence, in 3 years, Jack's father will be 76/2 = 38 years old.
It means that Jack's father is 38-3 = 35 years old now. ANSWER
Solved in this interpretation.
This problem is a good exercise, since it teaches a student to build a logical chain of steps.
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