Question

find the sum of the following Aps;
2,7,12,.....to 10 terms


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Answer 1

2, 7,12, .... 10 terms

We know that

Sum of Ap = n/2 ( 2a +( n - 1) d)

Here n=10, a=2 & d = 7-2 =2

10/2(2×2+ ( 10-1)×5

5( 3+9×5)

5(4+45)

Answer 2

ᴄʟᴇᴀʀʟʏ,ᴛʜᴇ ɢɪᴠᴇɴ sᴇǫᴜᴇɴᴄᴇ ɪs ᴀɴ AP ᴡɪᴛʜ ғɪʀsᴛ ᴛᴇʀᴍ.

ᴀ=2, ᴄᴏᴍᴍᴇɴ ᴅɪғғᴇʀᴇɴᴄᴇ D=5 ᴀɴᴅ N=10.

ɴᴏᴡ,

$s_{10} = \frac{10}{2} (2a + (10 - 1)d) \\ 5(2 \times 2 \times + 9 \times 5)$

$= 245$