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Is x<5 ? (1) x^2 > 5 (2) x^2 + x < 5

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Is x<5 ? (1) x^2 > 5 (2) x^2 + x < 5  [#permalink]

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New post 24 Jun 2017, 03:15
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Is x<5 ?

(1) x^2 > 5

(2) x^2 + x < 5

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Re: Is x<5 ? (1) x^2 > 5 (2) x^2 + x < 5  [#permalink]

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New post 24 Jun 2017, 03:37
1
2
AbdurRakib wrote:
Is x<5 ?

(1) \(x^2\)>5

(2) \(x^2\)+x<5


(1) \(x^2>5\)

If \(x = 6\) or\(-6\). \(x^2\) will be greater than 5 in both cases.

However 6 is greater than 5 and -6 is less than 5.

(1) has multiple values. Hence I is Not Sufficient.

(2) \(x^2+x<5\)

\(x(x+1) < 5\)

\(x<5\) or

\(x+1<5 = x < 4\)

(2) has x less than 5 or 4. Therefore x is less than 5. II is Sufficient. Answer (B)...
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Re: Is x<5 ? (1) x^2 > 5 (2) x^2 + x < 5  [#permalink]

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New post 24 Jun 2017, 03:44
1
AbdurRakib wrote:
Is x<5 ?

(1) \(x^2\)>5

(2) \(x^2\)+x<5



Solution:

Statement 1: x can be 3,4,5 or 10. Insufficient.

Statement 2: The greatest positive value that satisfies the equation is 1. Therefore, x<5 . Sufficient.

Answer is Option B.
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Re: Is x<5 ? (1) x^2 > 5 (2) x^2 + x < 5  [#permalink]

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New post 26 Jun 2017, 14:55
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1
Is x<5 ?

\((1) x^2 > 5\)

This means x can have Positive and Negative values , lets check

\(x = 10 = x^2 = 100\)

\(x = - 10 = x^2 = 100\)

As we are getting answer as YES & NO

Eq. (1) =====> is NOT SUFFICIENT

\((2) x^2 + x < 5\)

\(x^2 + x < 5\)

\(x(x + 1) < 5\)

\(x < 5\) or

\(x < 4\)

As both these values are < 5

(2) =====> is SUFFICIENT

Hence, Answer is B
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Re: Is x<5 ? (1) x^2 > 5 (2) x^2 + x < 5  [#permalink]

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New post 17 Nov 2017, 12:38
2
AbdurRakib wrote:
Is x<5 ?

(1) x^2 > 5

(2) x^2 + x < 5


We need to determine whether x < 5.

Statement One Alone:

x^2 > 5

If x = 3, then x is less than 5. However, if x = 6, then x is not less than 5. Statement one alone is not sufficient to answer the question.

Statement Two Alone:

x^2 + x < 5

Thus, we have x < 5 - x^2. Since x^2 is nonnegative, we have 5 - x^2 ≤ 5. Since x < 5 - x^2 and 5 - x^2 ≤ 5, we have x < 5.

Answer: B
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Re: Is x<5 ? (1) x^2 > 5 (2) x^2 + x < 5  [#permalink]

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New post 18 Nov 2017, 16:39
AbdurRakib wrote:
Is x<5 ?

(1) x^2 > 5

(2) x^2 + x < 5



Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

Since we have 1 variables and 0 equations, D is most likely to be the answer and so we should consider each of conditions first.

Condition 1)
\(x = 10\) : Yes
\(x = -10\) : No
This is not sufficient.

Condition 2)
\(x^2 + x < 5\)
\(x < 5 - x^2 < 5\)
This is sufficient.

Therefore, the answer is B.

If the original condition includes “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations” etc., one more equation is required to answer the question. If each of conditions 1) and 2) provide an additional equation, there is a 59% chance that D is the answer, a 38% chance that A or B is the answer, and a 3% chance that the answer is C or E. Thus, answer D conditions 1) and 2), when applied separately, are sufficient to answer the question) is most likely, but there may be cases where the answer is A,B,C or E.
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Re: Is x<5 ? (1) x^2 > 5 (2) x^2 + x < 5  [#permalink]

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New post 06 Apr 2018, 21:34
ydmuley wrote:
Is x<5 ?

\((2) x^2 + x < 5\)

\(x^2 + x < 5\)

\(x(x + 1) < 5\)

\(x < 5\) or

\(x < 4\)

As both these values are < 5

(2) =====> is SUFFICIENT

Hence, Answer is B


can anyone please solve the second statement in detail ?
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Is x<5 ? (1) x^2 > 5 (2) x^2 + x < 5  [#permalink]

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New post 06 Apr 2018, 23:27
1
pranavpal ,

St(2): \(x^{2} + x < 5\)

There are a couple of ways, we can solve the second statement.

Method1: Use Quadratic equation root formula:

For a given Quadratic equation \(ax^{2} + bx + c = 0\) (where \(a \neq 0\)), roots can be obtained using following frmula:

\(\frac{-b \pm \sqrt{b^{2} - 4ac}}{2a}\)

Lets first solve the equality case of st(2) i.e. : \(x^{2} + x -5 = 0\) . Here we have, a = 1, b = 1, c = -5. Put all the values in the above formula, we get:

Roots = \(\frac{-1 - \sqrt{21}}{2}, ~~~~ \frac{-1 + \sqrt{21}}{2}\) => approximately roots are -3 and +2.

In order to solve the inequality, put the root's value on the number line and check whether the inequality gets satisfied or not in each section.

----------------Not satisfy ----------(-3) --------Satisfy--------(2)--------Not satisfy------------

It is very clear that the st(2) will satisfy only when -3 < x < 2. => x is definitely less than 5. Hence, Sufficient.

I hope this helps.

Thanks.
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Re: Is x<5 ? (1) x^2 > 5 (2) x^2 + x < 5  [#permalink]

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New post 07 Apr 2018, 17:40
3
Although most of the folks got it right, I want to mention something which most of the folks got wrong..

x(x+1)<5

DOES NOT MEAN - x < 5 or (x+1) < 5.

and you easily check it by substitution

See bunuel's post - https://gmatclub.com/forum/inequalities ... 06653.html
Re: Is x<5 ? (1) x^2 > 5 (2) x^2 + x < 5 &nbs [#permalink] 07 Apr 2018, 17:40
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