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In a sequence of ten terms, each term (starting with the third term) is equal to the sum of the two previous terms. The seventh term is equal to 6. Find the sum of all ten terms.

 Jun 26, 2019
 #1
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The sum can be represented by :

 

a + (a + d)  + ( 2a + d) + ( 3a + 2d) + (5a + 3d) + (8a + 5d) + (13a + 8d) + (21a + 13d) + (34a + 21d) + (55d + 34d)  =   143a + 88d

 

And we know that   the  7th term  = 6, so

 

13a + 8d  =  6         multiply through by 11

 

143a + 88d  =  66

 

So....the sum is 66

 

cool cool cool

 Jun 26, 2019

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