May 17th, 2018, 02:19 AM  #1 
Senior Member Joined: Aug 2014 From: India Posts: 233 Thanks: 1  How to solve this crazy problem?
A Certain sum amounts to 41280 in 6 years and to 29760 in 2 years at S.I. Find the sum and the rate of interest? Answer is 24000 and 12% p.a Usually they used to give one P or one T (time). But here they gave two different amounts and two different times and asking me to find one sum and one rate of interest. I am totally confused. Please help me. 
May 17th, 2018, 03:15 AM  #2 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,305 Thanks: 2443 Math Focus: Mainly analysis and algebra 
You can form two equations each having the amount and the interest rate as variables. Using those equations, you can eliminate one variable and thus solve for the other. Substitute and solve for the remaining variable.

May 17th, 2018, 04:47 AM  #3 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,398 Thanks: 829 
a = start sum, r = rate Code: YEAR BALANCE 0 a 2 29760 = a + 2*a*r [Eq 1] 6 41280 = a + 6*a*r [Eq 2] 
May 17th, 2018, 09:34 AM  #4 
Senior Member Joined: Aug 2014 From: India Posts: 233 Thanks: 1 
Now should I have to eliminate R and find P?

May 17th, 2018, 09:42 AM  #5 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,398 Thanks: 829 
Yes, and EASY to do: 2 equations and 2 variables. Get to work! 
May 17th, 2018, 09:51 AM  #6  
Senior Member Joined: May 2008 Posts: 279 Thanks: 65  Beer soaked ramblings follow. Quote:
Ah Sir D, didst thou also forgot Ganesh' command for you to give a complete worked out solution instead of half baked cryptic clues that will force Ganesh to actually do some real work?  
May 17th, 2018, 09:01 PM  #7 
Senior Member Joined: Aug 2014 From: India Posts: 233 Thanks: 1 
I got the answer.

May 18th, 2018, 04:12 AM  #8 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,398 Thanks: 829 
Congratulations! Why don't you show your steps to solving, as it may help a student: this is main purpose of this site... 
May 18th, 2018, 04:33 AM  #9 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,305 Thanks: 2443 Math Focus: Mainly analysis and algebra  
May 18th, 2018, 05:37 AM  #10 
Global Moderator Joined: Dec 2006 Posts: 18,954 Thanks: 1601 
By subtraction, 11520 = 4ar, so 5760 = 2ar. Hence a = 29760  5760 = 24000, and so r = 5760/48000 = 0.12 = 12%. There are various other ways of solving the two equations. 

Tags 
crazy, problem, solve 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
This simple looking problem is making me crazy! Plz help!  bhaghpan  Number Theory  2  June 8th, 2016 05:07 PM 
This simple looking problem is making me crazy! Plz help!  bhaghpan  Linear Algebra  2  June 5th, 2016 04:30 PM 
New Crazy Member Here!  MystMage  New Users  3  November 29th, 2015 06:15 PM 
PLZZ help me solve this math!! going crazy  NUSRAT  Elementary Math  2  June 12th, 2012 08:34 AM 