16 votes 16 votes What is the average of all multiples of $10$ from $2$ to $198$? $90$ $100$ $110$ $120$ Quantitative Aptitude gatecse-2014-set2 quantitative-aptitude easy numerical-computation factors + – go_editor asked Sep 28, 2014 • edited Jun 7, 2018 by Milicevic3306 go_editor 3.5k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
Best answer 21 votes 21 votes $ a=10,l=190$ $ s=\dfrac{n(a+l)}{2}=\dfrac{19\times (200)}{2}=1900$ Average $=\dfrac{1900}{19}=100$ Ans. is 100 Correct Answer: $B$ aditi answered Jan 16, 2015 • edited Apr 25, 2019 by Naveen Kumar 3 aditi comment Share Follow See all 3 Comments See all 3 3 Comments reply Ayush Upadhyaya commented Jan 2, 2019 reply Follow Share It's an AP $10,20,.......190$ The average of an AP=$\frac{a_1+a_n}{2}=\frac{190+10}{2}$ 6 votes 6 votes Kuldeep Pal commented Jun 10, 2019 reply Follow Share Average in case of A.P. series average = (first + last) / 2 =(190+10)/2 = 100 1 votes 1 votes Kiyoshi commented Nov 21, 2021 reply Follow Share Yup that’s true because, Sum of N terms of A.P. = N/2 * ( a+ l ) {a = first term, l= last term} Average = Sum of all the terms / No. of terms = (N/2 (a + l)) / N = (a + l) / 2 = (first term + last term) / 2 0 votes 0 votes Please log in or register to add a comment.
7 votes 7 votes a=10 l=190 number of term=19 average of multiplae of 10= (n/2(2a+(n-1)d))/n (2*10+18*10)/2=100 ans=100 pankaj9310 answered Jan 2, 2015 pankaj9310 comment Share Follow See 1 comment See all 1 1 comment reply Manu Thakur commented Jan 5, 2015 reply Follow Share Average in case of A.P. series average = (first + last) / 2 =(190+10)/2 = 100 11 votes 11 votes Please log in or register to add a comment.
7 votes 7 votes 10+20+30... + 180+190. 10(1+2+3+..19) Sum of first n no => n*(n+1)/2 (10*19*20)/2 = 1900. Average = Sum / Total no = 1900/19 = (B) 100 Akash Kanase answered Nov 28, 2015 Akash Kanase comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes for finding average of any A.P. series just do (first term+last term)/2 in this question (10+190)/2 =100 Ankit Srivastava 7 answered Jan 25, 2018 Ankit Srivastava 7 comment Share Follow See 1 comment See all 1 1 comment reply chalam121 commented Apr 11, 2018 reply Follow Share Good Method 0 votes 0 votes Please log in or register to add a comment.