Question

29. Find the sum of first 10 terms of the AP 2, 7, 12.
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Answer 1

Answer:

245 is the answer the answer hope u can understand it

Answer 2

Given:-

• $\bf a = 2$
• $\bf a_{2} = 7$
• $\bf a_{3} = 12$
• $\bf n = 10$

:$\implies$$\bf common\:difference (d) = a_{2}-a$

:$\implies$$\bf common \:difference (d) = 7-2 = 5$

To find:-

• sum of 10 terms of this A.P

Formula:-

:$\implies$$\underline\red{\boxed{\bf S_{n} = \dfrac{n}{2}×[2a+(n-1)d]}}$

Solution:-

:$\implies$$\bf S_{10} = \dfrac{10}{2}×[2(2)+(10-1)5]$

:$\implies$$\bf S_{10} = 5[4+45]$

:$\implies$$\bf S_{10} = 5×49= 245$

hence, the sum of 1st 10 terms of this A.P is 245