Find the sum of the following AP: 115,112,110,... to 11 terms
Finding the sum of the given AP :
Given, n=11, a=115 and d=a2-a1=112-115=160
Sum of an AP (Sn) is given as,
Sn=n22a+(n-1)d=1122×115+(11-1)·160=112215+1060=112×930=3320
Therefore, the sum of the AP 115,112,110,... to 11 terms is 3320
Determine whether the following numbers are in proportion or not:
13,14,16,17