How many integers between 50 and 5000 are divisible 7?explain full
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- There are 448 numbers between 50 and 500 which is divisible by 7 . The first one is 56 and the last is 497 . So if there are 448 numbers and every seventh one is divisible by 7 , 448/ 7 = 64 . So , there are 64 numbers between 50 and 500 are divisible by 7 .
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➤ The required A.P is
56, 63, 70,.........., 497
⇉ a = 56
⇉ d = T2 - T1
⇉ d = 63 - 56
⇉ d = 7
⇉ Tn = a +(n-1)d
⇉ 497 = 56 + (n-1)7
⇉ 497-56 = (n-1)7
⇉ 441/7 = n-1
⇉ 63 +1 = n
⇉ n = 64 terms
➤ Sn = n/2 (a+l)
⇉ S 64 = 64/2 ( 56 + 497)
⇉ S 64 = 32 x 553
⇉ S 64 = 17,696
➤ Hence the sum of all integers between 50 and 500 divisible by 7 is 17,696
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