All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Numbers > Sequences
8th Term from Term Product (Posted on 2016-03-07) Difficulty: 3 of 5
The first three terms of sequence {C(n)} are 1440, 1716 and 1848. These are obtained by multiplying the corresponding terms of two arithmetic sequences:{A(n)} and {B(n)}.
Find the 8th term of {C(n)}

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Trial and Error (spoiler?) | Comment 1 of 5
1716 = 2^2 * 3 * 11 * 13
1848 = 2^3 * 3 * 7 *11

Divide by their Greatest Common Divisor, wghich is 12

This makes the terms (divided by 12) 

2^3 * 3 * 15
11*13
2*7*11

Guess that the 2nd terms (ignoring the 12) are 11 and 13
Guess that the 3rd term (ignoring the 12) is 14 and 11
Then the first term (ignoring the 12)  is 8 and 15, which works

So, C(n) = 12 * (5 + 3n) * (17 - 2n)
C(8) = 12 * 29 * 1 = 348

This solution might or may not be unique.  

C(n) = (w + xn)(y + zn)
So we have three equations with 4 unknowns.  
There are an infinite number of A(n) and B(n) which work.
But it is possible that they all lead to the same C(n)

  Posted by Steve Herman on 2016-03-07 12:14:24
Please log in:
Login:
Password:
Remember me:
Sign up! | Forgot password


Search:
Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (3)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:
Copyright © 2002 - 2024 by Animus Pactum Consulting. All rights reserved. Privacy Information