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78. The smallest and largest no. between 200 and 400 which are divisible by 7 is

0 2 Views | Posted 4 months ago
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    Answered by

    Payal Gupta | Contributor-Level 10

    4 months ago

    78. 7282005740014605643550491Smallest =200−4+7=203Largest =400−1=399

    So we can form an A.P. 203,203+7, …., 399-7, 399

    So, i.e. a = 203 and d = 7 

    l = 399

    ⇒a+(x−1)d=399

    ⇒203+(x−1)7=399

    ⇒(x−1)7=399−203

    ⇒x−1=1967

    ⇒x=28+1

    ⇒x=29

    Sum of the 29 number of the AP = Required sum = η2[a+l)

    =292[203+399]

    =292×602

    = 8729.

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