Thursday, 24 March 2016

[R] Reasoning Tricks - 2 [Cubes/Dices]

In this article I will take up CUBES/DICES. They may pose a problem to you if you are not good at imagining things in 3D. So let's begin.
Firstly you should know that there are 2 types of dice - Standard and Ordinary.
In a standard dice, the sum of opposite faces is 7 [Remember that], so if they ask which face is opposite to 2, you can say it is 7-2 = 5. But mostly the questions are from ordinary dice, where the sum is not 7.

There are various rules to solve the problems on dice -

1. If two sides of Dices are common
If two sides of cubes are common( has same numbers or symbols), then the remaining two will be opposite to each other.

2. If one side of Dices is common
If one side of given dices is common then list these sides (numbers on them) either in clock-wise or anti-clockwise. Comparing the numbers obtained from both dices will give you the opposite numbers.

3. If one side is common and it's place is same in both dices.

If one side is common in both cubes and its place is also same, then the remaining two sides of respective dices will be the opposite to each other.

Now let's move to a typical CGL question - 

In this question the face opposite to 2 is asked, so just look at each cube and list the neighbours of 2
From 1st cube :
Neighbours of 2 = 3,4                  ...(1)
From 2nd cube :

Neighbours of 2 = 1,3                  ...(2)
In the third cube '2' is not present, so we will skip this cube
From 4th cube :

Neighbours of 2 = 4,6                   ...(3)
Now merge all the three results and prepare a consolidated list of the neighbours

Neighbours of 2 = 1, 3, 4, 6
Note the number which is missing from the list. Here it is 5
So 5 is opposite to 2.
Answer : 5

Note : For each face, there are 4 neighbours and 1 opposite face. So make sure when you make the final consolidated list for a face, it has 4 neighbours [like our list contained 4 neighbours]

Next question

From the above figure, neighbours of 6 = 1,3,5
Note that there are only 3 neighbours in the list and hence we can't be sure of the face that is opposite to 6. Either it can be 2 or 4 (both are missing from the list)
When you encounter such situations, pick the face which is featured in most of the cubes. We can see that 3 is present in three of the cubes, so let's pick it.
Neighbours of 3 = 1, 4, 5, 6
From above data we can deduce that the face opposite to 3 is 2. Now since 2 is opposite to 3, it cant be opposite to 6. Hence the face opposite to 6 is 4
Answer : 4

Unfolded Cubes
Remember the following things when you get an unfolded cube

In short, no matter which figure of an unfolded cube is given in the question, the alternate faces are opposite to each other.
Now a SSC question - 
From the unfolded cube it is clear that-
Circle is opposite to Triangle
Square is opposite to Heart
Diamond() is opposite to Clubs()
(A) In option A we can see that triangle is shown adjacent to circle, but we know that they are opposite. Hence option A is wrong
(C) In option C, square is adjacent to heart, but they are opposite. Hence C is wrong
(D) In option D, diamond is adjacent to clubs, but they are opposite. Hence D is wrong.
Answer : (B)

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  1. nice bhaii...i have problem in series completion ...can u bro post this topic in your next segment

  2. hi prasanth,For english,maths,reasoning if I totally depend on kiran previous papers and for gk i will study only science part from lucent and ncert...can I expect 120 + marks

  3. You are a new emerging king of hacks in SSC...Please keep posting..:)

  4. Pls keep posting sir ... new post aftr 4days :( :

  5. आसमान टेसु हुआ। 🎊 धरती सब पुखराज 🌴 , मन सारा केशर हुआ, 🎄 तन सारा रितुराज 🎉,रंग-रंग राधा हुयी 🆒,कान्हा हुऐ गुलाल,व्रन्दावन होली हुआ 😜, सखिया रचे धमाल 💃, होली राधा-श्याम की,🎎 ओर ना होली कोई, जो मन रचा श्याम रंग,💝 रंग चड़े ना कोई 🌈,आप सभी को होली की रंगभरी ढेरों शुभकामनाऐ .

  6. Happy Holi bhai

    it has become our daily routine to chck ur blog for a new post frm ur side
    as ur last post was 4 days back, that is why Ms. Deepali Sharma is a li'l bit sad.
    and she is rightfully sad coz ur way of attempting d ques is vry vry gr8, and we all ur followers are trying our best to make it a part n parcel of our way of attempting ques and hopefully go on cracking CGL this year.

    I can understand u might hv been busy this festive season, but please keep posting regularly as 8th may (CGL Pre) is approaching very fast.

    Anxiously waiting for ur next post like all others.

    Thanks and regards

  7. Its like AMUL MACHO "bade aaram se"
    Thanx bro

  8. Thank u sir..... amazing post :) :)

  9. Sir one request.....if u can tell us some shortcut of counting number of triangles.

  10. i am not able to figure-out the opposite of 4 in "Unfolded cubes" figure-3 ...

    1. That was a typo...check the figure again :)

  11. If the sum of two no is 42 and their product is 437 then find the absolute difference between the no.? Sir will you plz solve this qus I m not understand how I made it

    1. You can solve such questions with hit and trial
      The product of the numbers is 437. This means the product of the unit digits of the two numbers will give you 7. So two cases are possible:
      1. 1*7 = 7
      2. 3*9 = 7 (the unit digit of 27)
      Now pick 2 numbers that satisfy this condition, i.e. either their unit digits should be 1 and 7, or 3 and 9. Moreover the product of the numbers should be 42.
      You will get the numbers as 23 and 19. So answer = 23-19 = 4

      You can solve this question with equations too
      (a+b)^2 - (a-b)^2 = 4ab
      Put a+b = 42 and ab = 437
      (a-b)^2 = 16
      Hence (a-b) = 4

    2. Super thank you sir and your explaintion trick was supereb

    3. Super thank you sir and your explaintion trick was supereb

  12. Sir in rule 2 , how 2 is opposite to 5 , but 5 not given in any dice so may be 2 is opposite to 2, its right or wrong , plz updated

    1. Cube is a 3-D object. Only three sides are visible from an angle. 5 is surely there at the back, you just cant see it. So 2 is opposite to 5.

  13. Sir I need your help in number series question. If you could Please upload something for that.

    1. and finding the wrong terms in number series.

  14. Sir plz provide coloured dice problem concepts

  15. Sir plz provide coloured dice problem concepts

  16. Sir in the question just above the unfolded to identify the number which occur most,bcoz 5 is also occured three times...i am not getting that point...plz explain

    1. You can take 5 as well. From that you will get that 5 is opposite to 1. Now look at cube no.2 and imagine "5" opposite to 1.
      Now compare cube No. 2 and 3 and apply Rule No.1
      You will get that 4 and 6 are opposite to each other.

  17. Really helpful.. great job sir.. Saves a lot of time

  18. Sir how do I solve the qwestion for the case of a dice which are in two forms and having no number in common.and it is not a standard dice..
    Plz explain it sir with suitable examples!
    Eagerly Waiting. 4 ur reply sir

  19. do you have any tricks on counting number of blocks sir?