Question

For an AP if a=6 d=3 then find S19​

Answer 1

Answer:

a=6d=3Sn=2n[2a+(n−1)d]S10=210[2×6+(10−1)3]=5[12+27]=5×39=195

Answer 2

Step-by-step explanation:

$a = 6 \\ d = 3 \\ n = 19 \\ S_{19} = \: \: ?? \\ \\ S_{n} = \frac{n}{2} ｛2a + (n - 1)d｝ \\ S_{19} = \frac{19}{2} ｛2 \times 6 + (19 - 1)3｝ \\ S_{19} = \frac{19}{2} ｛12 + (18) 3)｝ \\ S_{19} = \frac{19}{2} ｛12 + 54｝ \\ S_{19} = \frac{19}{_{1 \: \: } \cancel 2} \times \cancel {66} _{ \: \: 33} \\ S_{19} = \underline{ \underline{627}}$