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For how many values of x, is |||x - 5| -10| -5| = 2?

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New post 04 Jul 2012, 00:20
Eshaninan wrote:
Not using graphs:
Take |x-5| as "A" , |A-10| as "B"
then |B-5| = 2 would have 2 answers 7 and 3 for B
Now, take |A-10|=7, would give two solutions for A and |A-10|=3 would give 2 solutions for A
For each of these 4 solutions equate for |x-5| which would give 2 solutions for each equation and hence a total of 4*2 = 8 solution for x


Yes, you can do it this way too. But you have to be careful of the values given e.g.
In instead of 2, we have 0, you will get 4 solutions since |B-5| = 0 will give you only 1 value of B. Each of the subsequent values will give you 2 values each. I am not a big fan of multiple variables so I don't use them. Graphical approach just seems more intuitive to me.
Anyway, as long as you know what you are doing, you can use whatever method you like.
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Re: Question of the Day  [#permalink]

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New post 01 Dec 2012, 08:45
VeritasPrepKarishma wrote:
Question of the Day:

Q. For how many values of x, is lllx - 5l -10l -5l = 2?
(A) 0
(B) 2
(C) 4
(D) 8
(E) More than 8

(Those ls are mods)
(Earn kudos if you solve it in under 2 mins.)
Note: This question is beyond GMAT level. Nevertheless, it helps you understand mods and graphs and hence, is great for practice.)



Hi Karishma,
Your sig. in this post contains a link that says "Download the Veritas Prep GMAT On Demand App Free http://itunes.apple.com/us/app/gmat-on- ... 60224?mt=8".

But I think veritas Prep on Demand course is NOT available FREE to download on apple product.

Your thoughts on this..!!
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Re: Question of the Day  [#permalink]

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New post 06 Dec 2012, 05:33
Crazy question haha! But I had fun!

|||x-5|-10|-5| = 2

Let y = ||x-5|-10|
|y-5| = 2 gives us two values of y=7 and y=3

Let w = |x-5|
|w - 10|=7 or |w-10|=3
Each will give two values of w. Thus, we have 4 values of w: 17,3,13,7

|x-5|=17, x=22 and -12
|x-5|=3, x=8 and 2
|x-5|=13, x=18 and -8
|x-5|=7, x=12 and -2

Answer: 8
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Re: Question of the Day  [#permalink]

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New post 06 Dec 2012, 06:24
shortcut:

there are tow possible x for |x-z|=y as long as y=|=0 since the result can be either positive or negative.

therefore we have
2x2x2=8
possible solutions
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New post 06 Dec 2012, 21:55
debayan222 wrote:
Hi Karishma,
Your sig. in this post contains a link that says "Download the Veritas Prep GMAT On Demand App Free http://itunes.apple.com/us/app/gmat-on- ... 60224?mt=8".

But I think veritas Prep on Demand course is NOT available FREE to download on apple product.

Your thoughts on this..!!


The app is free. You can download it. The first lesson which discusses Test structure, scoring, pacing, myths, Veritas methodologies, typical Veritas class etc is free. Thereafter, you can choose the modules you want to work on. You will obviously need to pay for them. You can buy the modules you want instead of buying the whole course.
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Re: For how many values of x, is |||x - 5| -10| -5| = 2 is |||x?  [#permalink]

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New post 14 Feb 2014, 22:57
Hi , from my thinking i got 3 x values is |||x - 5| -10| -5| = 2 ,
Uisng x = 8 , 2 , -12
Steps 1 |x - 5| = | 8 - 5 | = 3
step 2 | 3- 10 | = | -7 | = 7
step 3 | 7 -5 | = | 2 | = 2 :-D

in same way with x values 2 , and -12
karishma can you pls see my approach and reply me back
but u myself i think iam wrong :( :(
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Re: For how many values of x, is |||x - 5| -10| -5| = 2 is |||x?  [#permalink]

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New post 16 Feb 2014, 21:07
kanusha wrote:
Hi , from my thinking i got 3 x values is |||x - 5| -10| -5| = 2 ,
Uisng x = 8 , 2 , -12
Steps 1 |x - 5| = | 8 - 5 | = 3
step 2 | 3- 10 | = | -7 | = 7
step 3 | 7 -5 | = | 2 | = 2 :-D

in same way with x values 2 , and -12
karishma can you pls see my approach and reply me back
but u myself i think iam wrong :( :(


How did you get the values 8, 2 and -12? Note that there are a total of 8 values that x can take. Check the solutions given on the previous page and the attachment I have provided with the graphical approach.
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Re: For how many values of x, is |||x - 5| -10| -5| = 2?  [#permalink]

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New post 25 Apr 2015, 19:34
solved but in 2:52 mins.. what is the least time consuming way to approach this question?
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Re: For how many values of x, is |||x - 5| -10| -5| = 2?  [#permalink]

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New post 11 Aug 2015, 15:56
Here is an alternative to the graphical method already posted:

Start from the outside:
|a-5| = 2, where a = ||x-5| - 10| => a = 7,3
|b-10| = 7,3 where b = |x-5| => b = 17, 3, 13, 7
finally
|x-5| = 17,3,13,7. at this point, you do not have to solve it. we have the pattern where we first had 2 solutions for the outer ||, 4 for for the inner ||, we can assume 8 is the solution.

if 7 was a valid answer and you used this method, you need to continue it one further step to make sure that the solution wasnt duplicated.
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Re: For how many values of x, is |||x - 5| -10| -5| = 2?  [#permalink]

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New post 13 Aug 2015, 06:24
1
VeritasPrepKarishma wrote:
Question of the Day:

For how many values of x, is |||x - 5| -10| -5| = 2?

(A) 0
(B) 2
(C) 4
(D) 8
(E) More than 8

(Those ls are mods)
(Earn kudos if you solve it in under 2 mins.)
Note: This question is beyond GMAT level. Nevertheless, it helps you understand mods and graphs and hence, is great for practice.)

|x-5| has two values, therefore 2 solutions
There are 3 mod
Hence 2^3 = 8 solutions
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Re: For how many values of x, is |||x - 5| -10| -5| = 2?  [#permalink]

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New post 22 Aug 2015, 05:06
shrouded1 wrote:
Easiest way is to graph it, which will immediately show exactly 8 solutions. Alternatively :
|x-5|=0 .. Exactly 1 solution at x=5
||x-5|-10|=0 .. Exactly 2 solutions at x=5-10=-5 & x=5+10=15
|||x-5|-10|-5|=0 .. Exactly 4 solutions at x=-5-5,-5+5,15-5,15+5 OR x=-10,0,10,20

At this point it is very easy to imagine what the graph looks like, it'll be 3 triangular humps touching the x-axis at the above points and going to +inf as x goes below -10 or above 20.
All the lines are at 45 degrees, so the peaks will be at y=5

Now |||x-5|-10|-5|=2 is just equivalent to shifting the x-axis up by 2 units, or counting the number of intersections with the y=2 line. Given the peaks are at y=5, there will be the maximum possible number of intersections, which is 8 in the following regions :

Below -10
Between -10 & -5
Between -5 and 0
Between 0 & 5
Between 5 & 10
Betweem 10 & 15
Between 15 & 20
Above 20

Answer is 8.

As already mentioned, if you just graph it out, this should be straight forward to see




Can you please draw a graph for this question. very weak in this topic :(
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Re: For how many values of x, is |||x - 5| -10| -5| = 2?  [#permalink]

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New post 22 Aug 2015, 05:12
1
dreamrunner wrote:
shrouded1 wrote:
Easiest way is to graph it, which will immediately show exactly 8 solutions. Alternatively :
|x-5|=0 .. Exactly 1 solution at x=5
||x-5|-10|=0 .. Exactly 2 solutions at x=5-10=-5 & x=5+10=15
|||x-5|-10|-5|=0 .. Exactly 4 solutions at x=-5-5,-5+5,15-5,15+5 OR x=-10,0,10,20

At this point it is very easy to imagine what the graph looks like, it'll be 3 triangular humps touching the x-axis at the above points and going to +inf as x goes below -10 or above 20.
All the lines are at 45 degrees, so the peaks will be at y=5

Now |||x-5|-10|-5|=2 is just equivalent to shifting the x-axis up by 2 units, or counting the number of intersections with the y=2 line. Given the peaks are at y=5, there will be the maximum possible number of intersections, which is 8 in the following regions :

Below -10
Between -10 & -5
Between -5 and 0
Between 0 & 5
Between 5 & 10
Betweem 10 & 15
Between 15 & 20
Above 20

Answer is 8.

As already mentioned, if you just graph it out, this should be straight forward to see




Can you please draw a graph for this question. very weak in this topic :(


Here is a graph of |||x - 5| -10| -5| = 2:
Attachment:
MSP55621c3692c156b65ec00004239b89491b925i9.gif
MSP55621c3692c156b65ec00004239b89491b925i9.gif [ 5.74 KiB | Viewed 1092 times ]


Theory on Abolute Values: math-absolute-value-modulus-86462.html
Absolute value tips: absolute-value-tips-and-hints-175002.html

DS Abolute Values Questions to practice: search.php?search_id=tag&tag_id=37
PS Abolute Values Questions to practice: search.php?search_id=tag&tag_id=58

Hard set on Abolute Values: inequality-and-absolute-value-questions-from-my-collection-86939.html


Hope it helps.
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Re: For how many values of x, is |||x - 5| -10| -5| = 2?  [#permalink]

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New post 24 Aug 2015, 00:01
dreamrunner wrote:
shrouded1 wrote:
Easiest way is to graph it, which will immediately show exactly 8 solutions. Alternatively :
|x-5|=0 .. Exactly 1 solution at x=5
||x-5|-10|=0 .. Exactly 2 solutions at x=5-10=-5 & x=5+10=15
|||x-5|-10|-5|=0 .. Exactly 4 solutions at x=-5-5,-5+5,15-5,15+5 OR x=-10,0,10,20

At this point it is very easy to imagine what the graph looks like, it'll be 3 triangular humps touching the x-axis at the above points and going to +inf as x goes below -10 or above 20.
All the lines are at 45 degrees, so the peaks will be at y=5

Now |||x-5|-10|-5|=2 is just equivalent to shifting the x-axis up by 2 units, or counting the number of intersections with the y=2 line. Given the peaks are at y=5, there will be the maximum possible number of intersections, which is 8 in the following regions :

Below -10
Between -10 & -5
Between -5 and 0
Between 0 & 5
Between 5 & 10
Betweem 10 & 15
Between 15 & 20
Above 20

Answer is 8.

As already mentioned, if you just graph it out, this should be straight forward to see



Can you please draw a graph for this question. very weak in this topic :(


Another graphical solution is given here: for-how-many-values-of-x-is-x-103766.html#p808780

However, note that if you are weak in this topic, you may not want to start out here. Check out the more basic discussions on this topic first. This question is beyond GMAT level.
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Re: For how many values of x, is |||x - 5| -10| -5| = 2?  [#permalink]

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New post 10 Nov 2015, 16:17
Hi Bunuel.
Actually I still can not understand the right framework for this kind of questions ( how many solutions of X - ranges in modulus and inequalities. when I make the expression -ve and when +ve in the multi expression questions. please help in this and try to focus on the basics and the main concept to be able to answer such kind of questions.
many thanks in advance.
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Re: For how many values of x, is |||x - 5| -10| -5| = 2?  [#permalink]

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Re: For how many values of x, is |||x - 5| -10| -5| = 2? &nbs [#permalink] 31 Mar 2018, 01:31

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