find the sum of 20 terms of an ap:2,5,8,11...
step by step explanation
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find the sum of 20 terms of an ap:2,5,8,11...
step by step explanation
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Verified answer
✬ S²⁰ = 610 ✬
Step-by-step explanation:
Given:
To Find:
Solution: Here ,
➮ a = 2 ( First term )
➮ d = 5 – 2 = 3 ( Common diffrence )
➮ n = 20 ( Number of terms )
As we know that
Sum of n terms of an AP a , a + d , a + 2d,......l is given by
★ Sn = n/2 { 2a + ( n – 1 ) d } ★
[tex]\implies{\rm }[/tex] S²⁰ = 20/2 {2 [tex]\times[/tex] 2 + (20 – 1)3
[tex]\implies{\rm }[/tex] S²⁰ = 10 { 4 + (19)3 }
[tex]\implies{\rm }[/tex] S²⁰ = 10 { 4 + 57 }
[tex]\implies{\rm }[/tex] S²⁰ = 10 [tex]\times[/tex] 61
[tex]\implies{\rm }[/tex] S²⁰ = 610
Hence, the sum of first 20 terms of the given AP is 610.
Answer:
Sum of 20terms of AP
SN = n/2( 2a +(n-1)d)
Here,,
A=2
D=3
N=20
S20=?
So,,,
[tex]s20 = 20 \div 2 (2 \times 2 + (20 - 1) \times 3 \\ then \\ s20 = 10(4 + 19 \times 3) \\ 10(4 + 57) \\ 10 \times 61 \\ s20 = 610[/tex]
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