May 5th, 2014, 06:44 AM  #1 
Senior Member Joined: Sep 2013 From: Earth Posts: 827 Thanks: 36  Progression
Can somebody explain this to me?

May 5th, 2014, 09:10 AM  #2 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,674 Thanks: 2654 Math Focus: Mainly analysis and algebra 
First of all, you should find a general formula for $H_n$ in terms of $H_{n1}$ only. You know that $H_1 = 0.8H$ and $H_2 = 0.8H_1$, does that suggest anything? Next you can use this formula to find an expression for $H_n$ in terms of $H$ only. Try making a list of $H_1, H_2, H_3, ...$ in terms of $H$. See if you can spot a pattern. How does $H_n$ change as $n$ increases? Do the $H_n$ increase or decrease? Now you can solve $H_n \lt 50$ for $n$. In the last part, you have to work out the sum that you should evaluate. Be careful! For all but the first $H$, the ball travels the distance on the way up as well as the way down. The big question here is how far do you have to sum the series? 

Tags 
progression 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Arithmetic Progression and Geometric Progression  jiasyuen  Algebra  1  May 1st, 2014 03:40 AM 
Progression .  jiasyuen  Algebra  5  April 23rd, 2014 04:36 AM 
progression  panky  Algebra  1  December 8th, 2011 09:32 AM 
progression  mikeportnoy  Algebra  3  October 14th, 2008 01:42 AM 
progression  mikeportnoy  Real Analysis  0  December 31st, 1969 04:00 PM 