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Science Section => Science General Discussion => Math and Computers => Topic started by: Solitary on August 28, 2014, 12:03:46 AM

Title: Do You Know The Answer?
Post by: Solitary on August 28, 2014, 12:03:46 AM
"My grandson is about as many days as my son is weeks, and my grandson is as many months as I am in years. My grandson, my son and I together are 120 years. Can you tell me my age in years?


Answer below, don't peek!













































"This problem is conveniently solved by writing down the necessary equations. Note that there are 12 months in a year, 52 weeks in a year, and 365 days in a year.

Let m be my age in years. If s is my son's age in years, then my son is 52s weeks old. If g is my grandson's age in years, then my grandson is 365g days old. Thus,

365g = 52s.

Since my grandson is 12g months old,

12g = m.

Since my grandson, my son and I together are 120 years,

g + s + m = 120.

The above system of 3 equations in 3 unknowns (g, s and m) can be solved as follows.

m / 12 + 365 m / (52 × 12) + m = 120 or

52 m + 365 m + 624 m = 624 × 120 or

m = 624 × 120 / 1041 = 72.

So, I am 72 years old."

Food for thought:

Why is the word "about" used in the Problem Statement in the sentence "My grandson is about as many days as my son is weeks"? Calculate the son's age and the grandson's age. Then, verify whether the first equation (i.e., 365g = 52s) is exactly satisfied.

An elegant solution is possible on realizing the significance of the word "about" in the Problem Statement.

Elegant Solution:

The first equation (365g = 52s) can be approximated by

7g = s.

As before, the other two equations are

12g = m

g + s + m = 120.

The above system of 3 equations in 3 unknowns (g, s and m) can be simply solved as follows.

g + 7g + 12g = 120 or 20g = 120.

m = 12g = 12 × 120 / 20 = 72.

So, Grandpa is 72 years old.
Title: Re: Do You Know The Answer?
Post by: GrinningYMIR on August 28, 2014, 11:44:45 AM
(http://media-cache-ak0.pinimg.com/736x/85/6f/24/856f241ceaabfcaa784311f8da046bb3.jpg)



Interesting problem, but my brain hurts now

*fetal position*
Title: Re: Do You Know The Answer?
Post by: Solitary on August 28, 2014, 12:05:49 PM
I just hated these types of story problems in school because they really do make your brain hurt. Mind is kind of numb now from all my prescription drugs---honestly!  :eek: :lol: Solitary
Title: Re: Do You Know The Answer?
Post by: Green Bottle on August 28, 2014, 12:16:27 PM

(http://media-cache-ak0.pinimg.com/736x/85/6f/24/856f241ceaabfcaa784311f8da046bb3.jpg)



Interesting problem, but my brain hurts now

*fetal position*

I just hated these types of story problems in school because they really do make your brain hurt. Mind is kind of numb now from all my prescription drugs---honestly!  :eek: :lol: Solitary

I read the question then................
I read it again and then i thought , fkit, scroll down an lets see the answer an as i started to read it i thought, mmmmmmm, have i got painkillers... :wall: :axe: (http://i62.tinypic.com/wtu6c1.gif)
Title: Re: Do You Know The Answer?
Post by: SGOS on August 28, 2014, 01:09:03 PM
Yeah, I just said, "Piss on it," and scrolled down to the bottom.
Title: Re: Do You Know The Answer?
Post by: PickelledEggs on August 28, 2014, 01:28:52 PM
I wasn't able to get that because I'm not a mathmagician