For class 10th math of arithmetic progressions of exercise 5.3 of math, how i solve this important question in easy way, Find the sum of first 51 terms of an AP whose second and third terms are 14 and 18, respectively.
AnilSinghBoraGuru
Find the sum of first 51 terms of an AP whose second and third terms are 14 and 18, respectively. Q.8
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Given that,
Second term, a2 = 14
Third term, a3 = 18
Common difference, d = a3−a2 = 18−14 = 4
a2 = a+d
14 = a+4
a = 10 = First term
Sum of n terms;
Sn = n/2 [2a + (n – 1)d]
S51 = 51/2 [2×10 (51-1) 4]
= 51/2 [2+(20)×4]
= 51 × 220/2
= 51 × 110
= 5610