Question 6

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Jambmaths question: 

Find the sum of the first 10 terms of the A.P, 3+10+17+….

Option A: 

345

Option B: 

415

Option C: 

321

Option D: 

315

Jamb Maths Solution: 

$\begin{align}  & a=3,\text{ }d=10-3=7 \\ & {{S}_{n}}=\tfrac{n}{2}[2a+(n-1)d] \\ & {{S}_{10}}=\frac{10}{2}[2\times 3+(10-1)7]=5[6+63] \\ & {{S}_{10}}=345 \\\end{align}$

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