Question:
Find 3+6+9+ ... + 180.
A5490
B4950
C5400
Dഇതൊന്നുമല്ല
Answer:
A. 5490
Explanation:
3+6+9+ ... + 180 can be considered as an arithmetic series.
· First term, a = 3
· Last term, tn = 180
· Common difference, d = 2nd term – 1st term
= (6-3)
= 3
· Number of terms, n = ?
To find the number of terms, we can use the formula to find the last term
tn
= a + (n-1) d
180 = 3
+ (n-1) 3
180 = 3
+ 3n – 3
180 = 3n
3n = 180
n = 180/3
n = 60
To find the total sum of the terms in an arithmetic
series,
Sn
= n/2 [2a + (n-1)d]
= 60/2 [(2x3)+(60-1)3]
= 30 [6+(59x3)]
= 30 x (6+177)
= 30 x
183
= 5490