Find sum to 15 terms of the A.P 13, 18,23…..?
Answers
Answer:
HEY MATE HOPE U ARE WELL...!
Step-by-step explanation:
Given : AP is 3, 8, 13, 18, 23 . . .
To find : Sum of its first 15 terms
Solution :
AP ( Arithmetic Progression ) is a sequence of numbers in which common difference between two consecutive terms is always same throughout every consecutive terms.
The general form of sum of n terms of AP is :-
Sn = n/2 [ 2a + (n - 1) d ]
Here,
Sn = Sum of n terms of AP
a = First term of AP
d = Common difference of AP
n = number of terms of AP
Common difference = a2 - a1
Common difference = 8 - 3
Common difference = 5
If we substitute n = 15 in the formula of sum of AP, we will get sum of it's 15 terms. Also substitute value of a and d.
→ S15 = 15/2 [ 2(3) + ( 15 - 1 )( 5 ) ]
→ S15 = 15/2 [ 6 + (14) (5) ]
→ S15 = 15/2 [ 6 + 70 ]
→ S15 = 15/2 [ 76 ]
→ S15 = 15 × 38
→ S15 = 570
Hence the sum of 15 terms of AP is 570.
Answer:
83
Step-by-step explanation:
a+14d
a= 13 and d= 18-13 =5
then a+14d
13+14*5=83