untitled

(Barré) #1
1200  1300  1400 ( 100 n 1100 )

(iii) In n-numbers of months, he deposits Tk. { 2 ( 1 ) }
2


a n d

n
 

= Tk. { 2 1200 ( 1 ) 100 }
2
u n


n

= Tk. ( 2400 100 100 )
2
 n


n
= Tk. 2 ( 1150 50 )
2
n

n
u 

= Tk. n( 50 n 1150 )
(iv) We know that 1 year = 12 months. Here n 12.
Therefore, A deposits in 1 year = Tk. 12 ( 50 u 12  1150 )
= Tk. 12 ( 600  1150 )
= Tk. 21 u 0517
= Tk. 21000.


Exercise 13.1




  1. Find the common difference and the 12th terms of the series
    2  5  12  19 




  2. Which term of the series 8  11  14  17  is 392?




  3. Which term of the series 4  7  10  13  is 301?




  4. If the pth term of an arithmetic series is p^2 and qth term is q^2 , what is
    (pq)th term of the series?




  5. If the mth tem of an arithmetic series is n and nth term is m, what is
    (mn)th term of the series?




  6. What is the number of n terms of the series 1  3  5  7 ?




  7. What is the sum of first 9 terms of the series 8  16  24 n?




  8. 5  11  71  23  95 What?




  9. 29  25  21  23 What?




  10. The 12th term of an arithmetic series is 7 7. What is the sum of the first 23 terms?




  11. If the 1 6 th term of an arithmetic series is  20 , what will be the sum of first 31
    terms?




  12. The total sum of first n terms of the series 9  7  5  is  144. Find
    the value of n.




  13. If the sum of first n terms of the series 2  4  6  8  is 25 50 , find the
    value of n.




  14. If the sum of first n terms of the series is n(n 1 ), find the series.




  15. If the sum of first n terms of the series is n(n 1 ), what is the sum of first 1 0
    terms?
    1 6. If the sum of 12 terms of an arithmetic series is 144 and first 20 terms is 560, find
    the sum of first 6 terms.



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