Question

t1=10,t10=30find the S10=?

Answer 1

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t = 10

$\mathtt{t_{10}=30}$

$\mathtt{30=10+9d}$

$\mathtt{30-10=9d}$

$\mathtt{\frac{20}{9}=d}$

$\mathtt{S_{10}=\frac{10}{2}(2(10)+(10-1) \times \frac{20}{9}}$

$\mathtt{S_{10}=5(20+20)}$

$\mathtt{S_{10}=200}$