Find the sum of all the integers which are multiples of 7 and lie between 200 and 400
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A = 203
An = 399
D = 7.
Now n=?
An = A + (n-1)D
399 = 203 + 7n - 7
7n = 399 - 196
7n = 203
n = 29
Now
S29 = 29/2 ( 203 + 399)
= 29 * 301
= 9010 - 301
= 8709.
An = 399
D = 7.
Now n=?
An = A + (n-1)D
399 = 203 + 7n - 7
7n = 399 - 196
7n = 203
n = 29
Now
S29 = 29/2 ( 203 + 399)
= 29 * 301
= 9010 - 301
= 8709.
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