1. Starting salary = a = Rs 5000 annual increment (common difference) = d = Rs 200 Let, after n years, his salary become Rs 7000. Therefore, a_n = 7000 ⇒ a + (n -1)d = 7000 ⇒ 5000 + (n - 1)(200) = 7000 ⇒ (n -1)(200) = 2000 ⇒ n - 1 = 10 ⇒ n = 11 Hence, in 11th year his salary become Rs 7000.

    Starting salary = a = Rs 5000 annual increment (common difference) = d = Rs 200
    Let, after n years, his salary become Rs 7000.
    Therefore, a_n = 7000
    ⇒ a + (n -1)d = 7000
    ⇒ 5000 + (n – 1)(200) = 7000
    ⇒ (n -1)(200) = 2000
    ⇒ n – 1 = 10 ⇒ n = 11
    Hence, in 11th year his salary become Rs 7000.

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  2. Let the first term of the AP = a and common difference = d According to first condition, a₄ + a₈ = 24 ⇒ a + 3d + a + 7d = 24 ⇒ 2a + 10d = 24 ⇒ a + 5d = 12 ⇒ a = 12 - 5d ...(1) According to second condition, a₆ + a_10 = 44 ⇒ a + 5d + a + 9d = 44 ⇒ 2a + 14d = 44 ⇒ a + 7d = 22 Putting the value of a frRead more

    Let the first term of the AP = a and common difference = d
    According to first condition, a₄ + a₈ = 24
    ⇒ a + 3d + a + 7d = 24
    ⇒ 2a + 10d = 24 ⇒ a + 5d = 12
    ⇒ a = 12 – 5d …(1)
    According to second condition, a₆ + a_10 = 44
    ⇒ a + 5d + a + 9d = 44
    ⇒ 2a + 14d = 44 ⇒ a + 7d = 22
    Putting the value of a from equation (1), we get
    (12 -5d) +7d = 22
    ⇒ 2d = 10 ⇒ d = 5
    Putting the value of d in equation (1), we get a = 12 – 5(5) = – 13
    The first three term of this AP: a, a + d, a + 2d = – 13, – 8, – 3.

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  3. Savings for the first week = a = Rs. 5 increment in saving = d = Rs. 1.75 Let, her saving become Rs. 20.75 after n weeks. Therefore, a_n = 20.75 ⇒ a + (n -1)d = 20.75 ⇒ 5 + (n -1)(1.75) = 20.75 ⇒ (n -1)(1.75) = 15.75 ⇒ n - 1 = 15.75/1.75 = 9 ⇒ n = 10 Hence, her saving become Rs 20.75, after 10 weeksRead more

    Savings for the first week = a = Rs. 5 increment in saving = d = Rs. 1.75
    Let, her saving become Rs. 20.75 after n weeks.
    Therefore, a_n = 20.75
    ⇒ a + (n -1)d = 20.75
    ⇒ 5 + (n -1)(1.75) = 20.75
    ⇒ (n -1)(1.75) = 15.75
    ⇒ n – 1 = 15.75/1.75 = 9 ⇒ n = 10
    Hence, her saving become Rs 20.75, after 10 weeks.

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  4. The 20th term from the last term of an AP: 3, 8, 13, ... 253 = the 20th term from the beginning of the AP: 253. 13, 8, 3. In the A.P.: 253, ..., 13, 8, 3, first term = 253 and common difference = 3 - 8 = -5 Therefore, a_20 = a + 19d ⇒ a_20 = 253 + 19(-5) = 253 - 95 = 158

    The 20th term from the last term of an AP: 3, 8, 13, … 253 = the 20th term from the beginning of the AP: 253. 13, 8, 3.
    In the A.P.: 253, …, 13, 8, 3, first term = 253 and common difference = 3 – 8 = -5
    Therefore, a_20 = a + 19d
    ⇒ a_20 = 253 + 19(-5) = 253 – 95 = 158

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  5. First term = 3 and common difference = 15 - 3 = 12 Let the nth term of AP: 3, 15, 27, 39 ... will be 132 more than its 54th term. Therefore, a_n = a₅₄ + 132 ⇒ a + (n -1)d = a + 53d + 132 ⇒ (n -1)(12) = 53 × 12 + 132 ⇒ (n -1)(12) = 768 ⇒ n -1 = 768/12 = 64 ⇒ n = 65 Hence, 65th term of the AP: 3, 15,Read more

    First term = 3 and common difference = 15 – 3 = 12
    Let the nth term of AP: 3, 15, 27, 39 … will be 132 more than its 54th term.
    Therefore, a_n = a₅₄ + 132
    ⇒ a + (n -1)d = a + 53d + 132
    ⇒ (n -1)(12) = 53 × 12 + 132
    ⇒ (n -1)(12) = 768
    ⇒ n -1 = 768/12 = 64
    ⇒ n = 65
    Hence, 65th term of the AP: 3, 15, 27, 39 . . . will be 132 more than its 54th trem.

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