Test: Arithmetic Series I - Ambitious

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Question 1:   Find the formula of the n-th term of an arithmetic progression   b n   :  a+3, a+1, a−1, a−3,…
b n =a−2n+4
b n =a−2n+1
b n =a−2n+5 
b n =a+2n+1
Question 2:   In the arithmetic progression (   a n   ):   a 1 =1; d=2.5  . Is  13.5  a term of this progression? If yes, find its number.
n=5
n=6
13.5  is not a term of this progression
n=13
Question 3:   Find the initial term of the arithmetic sequence (   a n   ), if   b 5 =11;   b 11 =−7  .
a 1 =23
a 1 =26
a 1 =19
More data is needed
Question 4:   What is the number of the first positive term of an arithmetic sequence (   a n   ): −10.2;−9.5;−8.8; …?
n=15
n=14
n=16
n=10
Question 5:   Find the first negative term of an arithmetic sequence (   a n   ):  7.2; 6.6; 6  .
−1.8
−0.1
−1.2
−0.6
Question 6:   Find the fourth term of an arithmetic progression (   a n   ) if   a 2 =−4.5;   a 7 =3  .
a 4 =−3
a 4 =−1.5
a 4 =−2
a 4 =0
Question 7:   The formula of an arithmetic progression (   a n   ) is   a n =−2n+1  . Find the sum of the first twenty terms of this progression.
s 20 =−400
s 20 =380
s 20 =−800
s 20 =−200
Question 8:   Find the sum of first fifteen terms of an arithmetic sequence (   a n   ), if   a 10 =44; d=4  .
s 15 =510
s 15 =1080
s 15 =540
s 15 =504
Question 9:   How many times (  N  ) a clock would stroke during a day if it strokes only integer amount of hours from  1  to  12  ?
N=12
N=78
N=156
N=24
Question 10:   Find the sum of all two-digit numbers that are multiples of  6  .
1620
804
816
810