doesn't specify arithmetic (or geometric) , but it comes out even
d = (55 - 29) / (22 - 9)
1st term = 29 - (9 d)
60th term = 1st term + (59 d)
sum = (1st term + 60th term) * (60 / 2)
The 9th and the 22nd term is 29 and 55 respectively. Find the sum of the first 60 terms
3 answers
you know that
d = (55-29)/(22-9) = 26/13 = 2
a = a9 - 8d = 29-16 = 13
S60 = 60/2 (2*13 + 59*2) = _____
d = (55-29)/(22-9) = 26/13 = 2
a = a9 - 8d = 29-16 = 13
S60 = 60/2 (2*13 + 59*2) = _____
oops ... 1st term = 29 - (8 d) ... not (9 d)
2 answers