The 20th term of arithmetic sequence 5,10,15...?sum of first 20 terms of arithmetic sequence 5,10,15...?sum of first 20 terms of arithmetic sequence 4,9,14...?
Answers
Answer:
Step-by-step explanation:
1) Sequence = 5, 10, 15,,,,,,
As we know that,
Sum of Nth term of an A.P.
⇒ Sₙ = n/2[2a + (n - 1)d].
First term = a = 5.
Common difference = d = b - a = c - b.
Common difference = d = 10 - 5 = 15 - 10.
Common difference = d = 5.
⇒ S₂₀ = 20/2[2(5) + (20 - 1)(5)].
⇒ S₂₀ = 10[10 + (19)(5)].
⇒ S₂₀ = 10[10 + 95].
⇒ S₂₀ = 10[105].
⇒ S₂₀ = 1050.
MORE INFORMATION.
Arithmetic progression.
If a is the first term and d is the common difference then A.P. can be written
as : a, a + d, a + 2d, a + 3d + ,,,,,
General term of an A.P.
General term (nth term) of an A.P. is given by,
Tₙ = a + (n - 1)d.
2)
let the (n) term = 20th
and, the common difference (d) =5
first term (a) = 4.
n = a + (n-1) * d.
n = 4 + (20 - 1 ) * 5
n = 4 + 19 * 5
n = 4 + 95
n = 99. answer
Answer:
Step-by-step explanation:
common difference 10 -- 5 = 5
First term - second term = Common difference
an = a=[n-1] x d
S20 = 5 + [20-1] x 5
S20 = 5+ 19 x 5 = 95
95 + 5 =
S20 = 100