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Mathematics

Fill in the blanks in the following table, given that a is the first term, d the common difference and an the nth term of the AP :

S.
No.
adnan
(i)738-----
(ii)-18----100
(iii)-----318-5
(iv)-18.92.5------3.6
(v)3.50105--------

AP

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Answer

(i) By formula,

an = a + (n - 1)d

Substituting values we get :

an = 7 + 3(8 - 1)

= 7 + 3 × 7

= 7 + 21

= 28.

Hence, an = 28.

(ii) By formula,

an = a + (n - 1)d

Substituting values we get :

⇒ 0 = -18 + (10 - 1)d

⇒ 0 = -18 + 9d

⇒ 9d = 18

⇒ d = 189\dfrac{18}{9} = 2.

Hence, d = 2.

(iii) By formula,

an = a + (n - 1)d

Substituting values we get :

⇒ -5 = a + (18 - 1)(-3)

⇒ -5 = a + 17 × -3

⇒ -5 = a - 51

⇒ a = 51 - 5 = 46.

Hence, a = 46.

(iv) By formula,

an = a + (n - 1)d

Substituting values we get :

⇒ 3.6 = -18.9 + (n - 1)(2.5)

⇒ 3.6 = -18.9 + 2.5n - 2.5

⇒ 3.6 = 2.5n - 21.4

⇒ 2.5n = 21.4 + 3.6

⇒ 2.5n = 25

⇒ n = 252.5\dfrac{25}{2.5} = 10.

Hence, n = 10.

(v) By formula,

an = a + (n - 1)d

Substituting values we get :

an = 3.5 + 0(105 - 1)

= 3.5 + 0 × 104

= 3.5 + 0

= 3.5

Hence, an = 3.5

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