find the sum of all natural number between 100 and 300 that are divisible by 7
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Answered by
1
heyyyy mate.....
thanks for the question...
ur ans is 5586 ...
hope it helps u....
thanks for the question...
ur ans is 5586 ...
hope it helps u....
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yohashini464:
steps
i do it by a trick on calci
wait i will show u the process
send the trick
okk
can u plz tell me the formula of sum
sn=n/2[a+l]
wait
now it is perfect
Answered by
2
the first number divisible by 7 after 100 is 105
the last number divisible by 7 before 300 is 294
Now we can project its as an AP
having A = 105 A n = 294 and. d = 7 obviously.
now A + (n-1)d = An
so 105 + (n-1)7 = 294
(n-1) 7 = 294 - 105
(n - 1 )7 = 189
n-1 = 189/7 = 27
n = 27+1 = 28
then using formula
Sn = n/2 [A + An]
= 28/2 [ 105 + 294]
= 14 [399]
= 3990 + 1596
= 5586
the last number divisible by 7 before 300 is 294
Now we can project its as an AP
having A = 105 A n = 294 and. d = 7 obviously.
now A + (n-1)d = An
so 105 + (n-1)7 = 294
(n-1) 7 = 294 - 105
(n - 1 )7 = 189
n-1 = 189/7 = 27
n = 27+1 = 28
then using formula
Sn = n/2 [A + An]
= 28/2 [ 105 + 294]
= 14 [399]
= 3990 + 1596
= 5586
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