Math, asked by jyotiguwalani8, 6 months ago

3. The first and last terms of an AP are 7 and 49 respectively. If sum of all
its terms is 420, find its common difference.
(3)
X
3​

Answers

Answered by kartik2507
0

Step-by-step explanation:

first term of AP = a = 7

last term of AP = l = a + (n - 1)d = 49

sum of the terms when last term is known

Sn = n/2 (a + l)

420 = n/2 (7 + 49)

420 = n/2 (56)

420 = 28n

n = 420/28

n = 15

l = a + (n-1)d = 49

7 + (15 - 1)(d) = 49

7 + 14d = 49

14d = 49 - 7

14d = 42

d = 42/14

d = 3

therefore the common difference = 3

Hope you get your answer

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