Q3 of 105 Page 146

In an AP :
given a = 5, d = 3, a_n = 50 find n and s_n

d is the common difference = 3

a is the first term = 5

a_n = 50

a_n = a + (n-1)d

50 = 5 + (n-1)(3)

45 = 3(n-1)

15 = n-1

n = 16

The sum of the series is S_n = [2a + (n-1) d]

= [ 2×5 + (16-1)(3)]

= 8 [ 55 ]

⇒ 440

Find the sums given below:

34 + 32 + 30 +….+10

Find the sums given below:

(-5) + (-8) + (-11) +…… + (-230)

In an AP :

given a = 7, a_n = 35 find d and s₁₃

In an AP :

given d = 3, a₁₂ = 37 find a and s₁₂

Questions · 105

6. Progressions

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In an AP :given a = 5, d = 3, an = 50 find n and sn