For sum of first 11 terms of the progression

we can use the formula:

n/2(2a+(n-1)d)

which will give us the value

50=2a+10d

also sum of progression is:

n/2[first term + nth term)

by that:

a1+a11=50

since it is mentioned in the question that the difference common difference d and the first term should be an integer then we can conclude that a1=5 and a11= 45 and the common difference d= 4 so the next term ie. a12 should be 49 so our answer here is 275+49=324

answer choice : D

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