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If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the

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Re: Value of M  [#permalink]

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New post 06 Dec 2015, 20:53
2
amithyarli wrote:
M = √4 + ∛4 + ∜4, then the value of M is ?

A. less than 3
B. equal to 3
C. between 3 and 4
D. equal to 4
E. greater than 4



Hi,
the most important point here is that any number >1, if put to any root(100th root or 200th root) will always have a value >1..
now lets see the equation..

M = √4 + ∛4 + ∜4...
we know √4=2 and both ∛4 and ∜4 will be >1..
s0 M=2+ something>1 +something>1..
or M is > than 4..
Ans E
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Re: If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the  [#permalink]

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New post 06 Dec 2015, 23:38
Forget conventional ways of solving math questions. In PS, IVY approach is the easiest and quickest way to find the answer.



If M=sqrt(4)+cuberoot(4) +sqrt(sqrt(4)) , then the value of M is:

A. Less than 3
B. Equal to 3
C. Between 3 and 4
D. Equal to 4
E. Greater than 4


We know that sqrt(4)=2.
Since 1^3=1 < (cuberoot(4))^3=4 < 2^3=8, 1<cuberoot(4)<2.
Similarly 1^4=4 < (sqrt(sqrt(4)))^4=4 <2^4=16 implies that 1<sqrt(sqrt(4))<2.
So 2+1+1<M<2+2+2.

M is between 4 and 6.

The answer is, therefore, E.
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Re: If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the  [#permalink]

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New post 07 Dec 2015, 09:23
1
Quote:

If M = √4 + ∛4 + ∜4, then the value of M is:

A) less than 3
B) equal to 3
C) between 3 and 4
D) equal to 4
E) greater than 4



√4
√4 = 2

∛4
∛1 = 1
∛8 = 2
So, ∛4 is BETWEEN 1 and 2.
In other words, ∛4 = 1.something

∜4
∜1 = 1
∜16 = 2
So, ∜ is BETWEEN 1 and 2.
In other words, ∜ = 1.something

So, √4 + ∛4 + ∜4 = 2 + 1.something + 1.something
= more than 4
= E

Cheers,
Brent
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Re: If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the  [#permalink]

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New post 21 Dec 2016, 06:56
zz0vlb wrote:
If \(M=\sqrt{4}+\sqrt[3]{4}+\sqrt[4]{4}\), then the value of M is:

A. Less than 3
B. Equal to 3
C. Between 3 and 4
D. Equal to 4
E. Greater than 4


\(M=\sqrt{4}+\sqrt[3]{4}+\sqrt[4]{4}\)


Or, \(M=2+2\sqrt{2}+\sqrt{2}\)

Now, \(2+2\sqrt{2} = 4.xx\)

Hence, the correct answer will always be > 4

Answer will be (E) Greater than 4
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Re: If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the  [#permalink]

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New post 11 Feb 2017, 21:30
Bunuel wrote:
zz0vlb wrote:
If \(M=\sqrt{4}+\sqrt[3]{4}+\sqrt[4]{4}\), then the value of M is:

A. less than 3
B. equal to 3
C. between 3 and 4
D. equal to 4
E. greater than 4


Here is a little trick: any positive integer root from a number more than 1 will be more than 1.

For instance: \(\sqrt[1000]{2}>1\).

Hence \(\sqrt[3]{4}>1\) and \(\sqrt[4]{4}>1\) --> \(M=\sqrt{4}+\sqrt[3]{4}+\sqrt[4]{4}=2+(number \ more \ then \ 1)+(number \ more \ then \ 1)>4\)

Answer: E.


Thank you Bunuel! :-D
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Re: If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the  [#permalink]

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New post 17 Feb 2018, 13:30
shrouded1 wrote:
udaymathapati wrote:
Please explain the answer.

Attachment:
Image2.JPG


\(M=4^{1/2} + 4^{1/3} + 4^{1/4}\)

Now we know that \(4^{1/2} = 2\)

We also know that \(4^{1/4} = \sqrt{2} \approx 1.414 > 1\)

And finally \(4^{1/3} > 4^{1/4} \Rightarrow 4^{1/3}>1\)

So combining all three together \(M > 2+1+1 \Rightarrow M > 4\)



How can it \(4^{1/4}\) be \(\sqrt{2}\) :? what function does exponent 1/4 have :?

\(\sqrt{2}\) without 1/4 exponent equals aprox 1.414
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Re: If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the  [#permalink]

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New post 17 Feb 2018, 14:12
1
dave13 wrote:
shrouded1 wrote:
udaymathapati wrote:
Please explain the answer.

Attachment:
Image2.JPG


\(M=4^{1/2} + 4^{1/3} + 4^{1/4}\)

Now we know that \(4^{1/2} = 2\)

We also know that \(4^{1/4} = \sqrt{2} \approx 1.414 > 1\)

And finally \(4^{1/3} > 4^{1/4} \Rightarrow 4^{1/3}>1\)

So combining all three together \(M > 2+1+1 \Rightarrow M > 4\)



How can it \(4^{1/4}\) be \(\sqrt{2}\) :? what function does exponent 1/4 have :?

\(\sqrt{2}\) without 1/4 exponent equals aprox 1.414


\(4^{\frac{1}{4}}=(2^2)^{\frac{1}{4}}=2^{\frac{2}{4}}=2^{\frac{1}{2}}=\sqrt{2}\)
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If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the  [#permalink]

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New post 08 Mar 2018, 15:19
zz0vlb wrote:
If \(M=\sqrt{4}+\sqrt[3]{4}+\sqrt[4]{4}\), then the value of M is:

A. Less than 3
B. Equal to 3
C. Between 3 and 4
D. Equal to 4
E. Greater than 4

Main idea:Approximate RHS by taking the cube root.

Details:

We have M= 4^ (1/3) + 4^ (1/3)+ 4^ (1/3) which is greater than 4

Hence E.
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Re: If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the  [#permalink]

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New post 12 Mar 2018, 15:35
zz0vlb wrote:
If \(M=\sqrt{4}+\sqrt[3]{4}+\sqrt[4]{4}\), then the value of M is:

A. Less than 3
B. Equal to 3
C. Between 3 and 4
D. Equal to 4
E. Greater than 4


We are given that M = √4 + ^3√4 + ^4√4. We need to determine the approximate value of M.

Since √4 = 2, we need to determine the value of 2 + ^3√4 + ^4√4

Let’s determine the approximate value of ^3√4. To find this value, we need to find the perfect cube roots just below and just above the cube root of 4.

^3√1 < ^3√4 < ^3√8

1 < ^3√4 < 2

Let’s next determine the approximate value of ^4√4. To find this value, we need to find the perfect fourth roots just below and just above the fourth root of 4.

^4√1 < ^4√4 < ^4√16

1 < ^4√4 < 2

Since both ^3√4 and ^4√4 are greater than 1, so √4 + ^3√4 + ^4√4 > 2 + 1 + 1, and thus, √4 + ^3√4 + ^4√4 > 4.

Answer: E
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Re: If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the  [#permalink]

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New post 16 Oct 2018, 05:27
I found this method much easier.
M= 4^1/2+ 4^1/3 + 4^1/4
=4^(1/2+1/3+1/4)
After taking LCM of 4^ the numbers, we get

=4^(36/12)
=4^3 which is greater than 4.
Answer is option E.

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Re: If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the  [#permalink]

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New post 16 Oct 2018, 06:23
topper97 wrote:
I found this method much easier.
M= 4^1/2+ 4^1/3 + 4^1/4
=4^(1/2+1/3+1/4)
After taking LCM of 4^ the numbers, we get

=4^(36/12)
=4^3 which is greater than 4.
Answer is option E.

Posted from my mobile device


That's totally wrong: \(a^x + a^y \neq a^{x+y}\)
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Re: If M=(root)(4)+(cube root)(4)+(fourth root)(4), then the &nbs [#permalink] 16 Oct 2018, 06:23

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