# Aptitude - Average - Discussion

### Discussion :: Average - General Questions (Q.No.11)

11.

The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is:

 [A]. 17 kg [B]. 20 kg [C]. 26 kg [D]. 31 kg

Explanation:

Let A, B, C represent their respective weights. Then, we have:

A + B + C = (45 x 3) = 135 .... (i)

A + B = (40 x 2) = 80 .... (ii)

B + C = (43 x 2) = 86 ....(iii)

Adding (ii) and (iii), we get: A + 2B + C = 166 .... (iv)

Subtracting (i) from (iv), we get : B = 31. B's weight = 31 kg.

 Shree Hema said: (Feb 13, 2011) A+B+C=45*3=>A+B+C=135----(1) A+B=40*2=>A+B=80----(2) B+C=43*2=>B+C=86----(3) Sub 3 in 1 A+86=135 A=41 Sub A value in 2 we get 41+B=80 B=31 Is this correct.. Pls anyone Reply me..

 Kantha said: (Feb 21, 2011) Ya. Its 100% right. There will be many ways to get answers for aptitude questions. No worries.

 Anil said: (Jun 29, 2011) A+B+C=45*3=>A+B+C=135----(1) A+B=40*2=>A+B=80----(2) B+C=43*2=>B+C=86----(3) S0 80+86-135=31 B=31

 Rsm said: (Jul 28, 2011) Anyone explain the logic behind it. Thanks in advance.

 M.V.Krishna/Palvoncha said: (Sep 9, 2011) Hello Rsm: Given data: avg. of A,B,C is 45, i.e.(A+B+C)/3=45, =>A+B+C=135....................(1) avg. of A,B is 40, i.e. (A+B)/2=40, =>A+B=80.......................(2) avg. of B,C is 43, i.e (B+C)/2=43, =>B+C=86.......................(3) from (1) & (2), we get C=55, from (1) & (3), we get A=49, subst. A & C in (1). we get B=31.

 Mandeep Sharma said: (Oct 23, 2011) so simple brother.... A+B+C= 45*3=135......1 A+B= 40*2= 80..........2 B+C= 43*2=86.......3 BY SUBTRACTING 1 FROM 2 WE GET 135-80= C=55, THEN PUT VALUE OF C IN 3.... B=86-55= 31.

 Pradeep said: (Nov 29, 2011) @shree hema. You said simple method. Thanks.

 Kaustubh L said: (Sep 7, 2013) A+B+C = 45*3 = 135---(1). A+B = 80. Hence (1) becomes: 80+C = 135. C = 55. B+C = 43*2 = 86. B = 86-55 = 31.

 Rabindra said: (Nov 12, 2013) Most simply answer: We know that, A+B+C/3 = 45. =>A+B+C = 135 .......(i). A+B/2 = 40 ........(a). B+C/2 = 43 ........(b). Add equation 'a' and 'b'. => (A+B/2)+(B+C/2) = 86. => (A+2B+C)/2 = 86. => A+B+C = 166 ........(ii). Subtract equation (ii) to (i) we get value of 'B'. B = 166 - 135 = 31. B = 31(answer).

 Ankur said: (Apr 17, 2014) Simplified. Sum of weights = 45*3 = 135. A+B+C = (45*3). A+B = (40*2)----1. B+C = (43*2)----2. From 1, 80+C=135 => c=55. from 2, B+55=86=> B=31.

 Jay Jadhao said: (Apr 22, 2014) No * Avg = Sum. 3 * 45 = 135. 2(A,B)* 40 = 80. 2(B,C)* 43 = 86. B= 86 - (135 - 80)= 31.

 Aliyaz said: (Aug 16, 2014) A+B+C = 45*3. A+B = 80. B+C = 86. We want 'B', So A+B+C-(A+B)-(B+C). => A+B+C-A-B-B-C = 135-80-86. => -B = -31. => B = 31.

 Varsha said: (Sep 9, 2014) @Shree hema when we subtract 135-86, Then result will be 49.

 Mayur said: (Oct 6, 2014) The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is: Let A, B, C represent their respective weights. Then, we have: A + B + C = (45 x 3) = 135 .... (i). A + B = (40 x 2) = 80 .... (ii). B + C = (43 x 2) = 86 ....(iii). Adding (ii) and (iii), we get: A + B+ B + C = 80+86 .... (iv). i.e B+A+B+C =166. But A + B + C = 135 so B+(A+B+C)=166 i.e B+135=166 then B=166-135. Subtracting (i) from (iv), we get : B = 31. B's weight = 31 kg.

 Priyanka said: (Aug 30, 2015) A+B+C = 135---- (1). A+B = 80---- (2). B+C = 86---- (3). Substitute (3) in (1). A+86 = 135. A = 49. Substitute A in (2). 49+B = 80. B = 80-49. B = 31.

 Munj said: (Oct 2, 2015) Explained answer is perfect by using elimination method.

 Nayab said: (Feb 23, 2016) If we add equation 1 and 3, we get 135 plus 86 = 221. So how it can be 166?

 Roshan said: (Mar 1, 2016) When average is 45 all three so why multiply by three.

 Prabakaran said: (Jul 9, 2016) a + b + c/3 = 45. a + b + c = 135------>1. We know b + c = 86. substitute in eqn 1. We get a + 86 = 135. a = 49. a + b/2 = 40. 49 + b = 80. b = 31 //. Answer.

 Avneet said: (Aug 30, 2016) A + B + C = 45 * 3 = 135. A + B = 40 * 2 = 80. B + C = 43 * 2 = 86. Now, (A + B + C ) - (A + B) = C i.e. 55, Vice versa for the value of A i.e. 49. Substitute the value of A in A + B = 80. B will be 31.

 Sara said: (Sep 13, 2016) Thanks, @Krishna. Your explanation was useful.

 Faisal said: (Mar 2, 2017) Thanks @Priyanka.

 Anjum said: (Mar 7, 2017) Thanks, it is easy to access the answers.

 Ayisha said: (Mar 7, 2017) Exactly right. Thank you all.

 Anjum said: (Mar 14, 2017) Thanks everyone for helping it by giving the explanation.

 Medha said: (Apr 13, 2017) B + c = 86 ( 1) A + B + C = 135 (2) A + B = 80 (3) Substituting (1) in (2) A = 135 - 86 = 49. From (3): B = 80 - 49 = 31.

 Thorat Sandip said: (Jul 5, 2017) A+B+C=135......(1) B+C=86.....(2) SUBTRACT EQ. 2 FROM 1, WE GET. (A+B+C)-(B+C)=135-86=49. A=49. A+B=80.....(3). PUT THE VALUE OF A IN ABOVE EQUATION. 49+B=80, B=80-49=31.

 Drukyul said: (Aug 1, 2017) A+B+C=135.......(1) B+C=86..............(2) A+B=80..............(3) A+86=135. A=49....................(4) Sub equ 4 in 3. 49+B=80, B=80-49, B=31.

 Ganeshgore said: (Sep 25, 2017) Thanks @Kaustubh.

 Raj Tiwari said: (Feb 6, 2018) Very easy and best trick, understand the average as equal distribution of data. As average of A,B,C = 45. means all is 45. a+b is 40 , but as both should be 45, means someone took 5 from both to make them 40. means 10 is taken so keep value -10 in mind. Similarly for a+c = 43 , 2 is less so someone taken 2 from.both means -4 is been taken from both. So.from both case 10 and 4. -14 is been taken. . And as b is the question lets make b as the robbery and if the average should be 45 and as b taken 14 from them. means b is 45-14 = 31.

 Raja Sadhukhan said: (Aug 23, 2018) The average weight of A B and C is 45*3=135, A,B is 2 person so 40*2=80, B and C-43*2=86, (80+86)-135, = 31.

 Dora said: (Oct 12, 2018) ABC is (45*3)=135, AB is (40*2)=80, BC is (43*2)=86. Now; A+B+C=135, '-----' +C=135, 80+C=135, C=135-80, C=55. So,B+C=86. B+55=86. B=31.

 Bhuwan Joshi said: (Jan 23, 2019) @Shree Hema. 135-86 = 49 not 41, than 49+ B=80, So, B=31 Years.

 Sidhu said: (Apr 18, 2019) A+B+C=45*3 PERSONS. A+B=40. B+C=43. SO; (A+B)+(C+B) = 40+43 = 83, A+2B+C = 83 * 2 = 166, B = 166 - 135 = 31.

 Arpit said: (Sep 11, 2020) Nice solution. Thanks all.

 Sandeep said: (Feb 5, 2021) Thanks @Shree Hema.

 Sangay said: (Aug 24, 2021) A + B + C = 45kg = 3 * 45 = 135, A+B=40kg=2*40 = 80. B+C=43kg=2*43 = 86. Therefore, 80 + 86 = 166. 166-135 = 31.