2
Q:
A) 11 days | B) 15 days |
C) 13 days | D) 16 days |
Answer: A) 11 days
Explanation:
Explanation:
Let 'n' number of days it take to complete.
we know that sum of n number= n/2[2a+(n-1)d]
where a=20,d=1;
n/2[2x20+(n-1)1]=275
n[n+39]=550
+ 39n - 550 = 0
+ 50n - 11n - 550 = 0
(n-11) (n-50) = 0
n-11 = 0;
n = 11(Days).