Monday, 9 May 2016

[Q] Averages Tricks - 1

Q. 1) The average weight of 4 men is increased by 3 kg when one of them who weighs 120 kg is replaced by another man. What is the weight of the new man?

Weight of new person = Weight of removed person + No. of persons * Increase in Average = 120+3*4
Weight of new person = 132 kg

Q. 2) The average marks obtained by 120 candidates in a certain examination is 35. If the average marks of passing candidates is 39 and that of the failed candidates is 15, what is the number of candidates who passed the exam?

Such questions are best dealt with allegation formula:
Mean value = 35, Dearer value = 39 and Cheaper = 15
Failed students : Passed students = (Dearer - Mean) : (Mean - Cheaper) = 39 - 35 : 35 - 15 = 4 : 20
No. of students who passed = (5/6) * 120 = 100

Q. 3)

Correct Average = Incorrect average + (Correct value - Incorrect value)/Total observations
Correct Average = 35 + (85 - 45)/20 = 37
Answer: (D)

Q. 4)

Take x = 1
Then A = (1 + 1)/2 = 1
Average of x^3 + 1/x^3 = (1 + 1)/2 = 1
Now put A = 1 in all the four options and check which one is giving '1' as the output
Answer: (D)

Q. 5)


For consecutive numbers:
If the number of terms is odd (e.g. A, B, C), then their average is the middle term(i.e. B).
If the number of terms is even(e.g. A, B, C, D) then their average is (B+C)/2
So here, the average of eight consecutive even numbers = (5th term + 4th term)/2
Given, (5th term + 4th term)/2 = 93
5th term + 4th term = 186
We know, 5th term - 4th term = 2
Adding the equations, we get 5th term = 94
Hence 8th term = 5th term + 2 + 2 + 2 = 100
Answer: (C)


Q. 6)

Average = (8*3 + 20*2 + 26*m + 29*1)/(3 + 2 + m + 1)
17 = (93 + 26m)/(6 + m)
102 + 17m = 93 + 26m
m = 1
Answer: (A)


Q. 7)

Given, (3a + 4b)/2 > 50
3a + 4b > 100
5a > 100  [Since a = 2b]
a > 20
Hence the smallest value of a is 21
Answer: (D)

Q. 8)

Average of six numbers a,b,c,d,e,f = (Average of a,b + Average of c,d + Average of e,f)/3
3.95*3 = 3.4 + 3.85 + x
x = 4.6
Answer: (C)


Q. 9) The average of 11 numbers is 50. The average of first six numbers is 49, and that of last six is 52. Find the sixth result.
This is a common CGL question and a short-cut to solve it is:
Sixth result = 50 + 6{(52 - 50) + (49 - 50)} = 50 + 6(2 - 1) = 56
Answer: 56


Q. 10)

Answer: (B)



Q.11)




If you have any doubt in this article, please drop a comment...
Keep reading :)

To buy the super-hit SSC Hack-Book, follow the below link-
Buy SSC Hack-Book

35 comments:

  1. Most awaited topic .m...
    Thanx a lot

    ReplyDelete
  2. Thanks a lot sir. A question continuously haunting in my mind what will be the safe score to get any post in cgl tier1 + tier 2. Can you share your tier 2 score and how you managed English exam in tier 2. Thanks

    ReplyDelete
  3. Thanks a lot sir. A question continuously haunting in my mind what will be the safe score to get any post in cgl tier1 + tier 2. Can you share your tier 2 score and how you managed English exam in tier 2. Thanks

    ReplyDelete
  4. Thanku so much sir...your topics helping a lot ...

    ReplyDelete
  5. if 15 men or 24 women or 36 boys can do a piece of work in 12 days, working 8hrs a day, how many men must be associated with 12 women and 6 boys to do another piece of work 6 times as great in 30 days working 6 hrs a day?
    Sir plz help me out in this problem

    ReplyDelete
  6. M1 = 15, H1 = 8, D1 = 12, W1 = 1
    M2 = X, H2 = 6, D2 = 30, W2 = 6
    M1*D1*H1/W1 = M2*D2*H2/W2
    X = 48
    48 men are required to finish the job
    But we already have 12 women and 6 boys
    1 woman = 5/8 man
    1 boy = 5/12 man
    Hence 12 women + 6 boys = 15/2 men + 5/2 men = 10 men
    Required no. of men = 48 - 10 = 38

    ReplyDelete
  7. prashant...can you suggest any good book that will be enough to cover di part for ssc cgl as well as sbi po !!

    ReplyDelete
  8. This comment has been removed by the author.

    ReplyDelete
  9. if pq+qr+rp=0 then find the value of p^2/p^2-qr +q^2/q^2-rp + r^2/r^2-pq
    sir is question ka shortcut bataiye

    ReplyDelete
  10. Hello Sir!!....
    pl. tell hw to solve dz ques.??
    Q. Ifa+1/b=1 and b+1/c=1 thn value of a.b.c is????
    pl. rpl.

    ReplyDelete
    Replies
    1. This comment has been removed by the author.

      Delete
    2. a+1/b=1
      =>ab=b-1...(1)

      b+1/c=1
      =>1/c = 1-b
      =>c=1/(1-b) ...(2)

      Multiply (1) and (2)

      abc = (b-1)*1/(1-b)
      =>abc = -1

      Delete
  11. [CGL 2014]
    (Please suggest a faster way to solve this)
    Q. If x=√5 + 2, then the value
    (2x^2-3x-2)/(3x^2-4x-3) is equal to

    1. 0.185
    2. 0.525
    3. 0.625
    4. 0.785

    I solved this the general way. By Putting the values of x and x^2 in the expression and then calculating it.

    ReplyDelete
  12. This comment has been removed by the author.

    ReplyDelete
  13. Sir how to solve
    this
    a+b+c= 1
    ab+bc+ca= 2
    abc=3 then find the value of
    1/(a+bc) +1/(b+ca) +1/(c+ab)

    ReplyDelete
  14. SIR PLZ ALSO POST IN HINDI

    ReplyDelete
  15. SIR PLZ ALSO POST IN HINDI

    ReplyDelete
  16. Sir pls ek post man chldrn women work p bhi bna de ...thnkyou

    ReplyDelete
  17. This comment has been removed by the author.

    ReplyDelete
  18. in 2nd question..from where 5/6 came?

    ReplyDelete
    Replies
    1. In that question,last ratio was 4:20 i.e 1:5
      from there no of passed students=5/5+1=5/6..i hope,now it is clear to you.

      Delete
  19. hi prashant,

    In 2nd question ,from where we got 5/6

    ReplyDelete
  20. SSC CGL-SSC CGL test Pattern 2016 has been released by the SSC and also the candidates ought to check it before going on to prepare for the examination on career chamber portal . career chamber provide full information of SSC CGL 2016.

    ReplyDelete
  21. sir in 9th question 1 term is common in both first and last 6 terms averages..if that term will not be included..then what will be shortcut??like
    Q)the average of 25 results is 18.the average of first 12 of them is 14&that of last twelve is 17.find the 13th result..

    ReplyDelete
  22. This comment has been removed by the author.

    ReplyDelete
  23. Sir would u plz tell me how 3 4 5 comes from

    ReplyDelete
  24. How in quesn. 5 , 5th - 4th term = 2 ?

    ReplyDelete