SOLUTION: the first term of arithmetic progression is 3. Given that the sum of the first 6 terms is 48 and that the sum of all the terms is 168,calculate the common difference,the number of
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Question 864059: the first term of arithmetic progression is 3. Given that the sum of the first 6 terms is 48 and that the sum of all the terms is 168,calculate the common difference,the number of terms in the sequence, and the last term Answer by richwmiller(17219) (Show Source):
You can put this solution on YOUR website! S = ½(2a + (n-1)d)n
48 = ½(6 + (5)d)6,
168 = ½(6 + (n-1)d)n
d = 2, n = 12
an = a + (n - 1)d
a12 =3 + (11)2
a12=25
check
S = ½(a + an)n
S = ½(3 + 25)12=168
ok
