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galiya
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When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] 06 May 2012, 08:28
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D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

55% (hard)

Question Stats:

55% (01:17) correct 45% (01:15) wrong based on 733 sessions

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When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] = ?

A. [22]
B. [44]
C. [45]
D. [88]
E. [90]
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D
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Bunuel
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When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] 06 May 2012, 10:13
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Galiya
When X is even, [x]=a/2+1, when X is odd [x]=2a+1 then [7]*[4]=?

A. [22]
B. [44]
C. [45]
D. [88]
E. [90]

your thoughts?
i went with C and was happy till didn't see the official answer
Show more

[7]*[4]=(2*7+1)(4/2+1)=45.

Now, notice that the answer choices are also in boxes, so we have that [x]=45, which means that for even x it should be 45=x/2+1 --> x=88=even and for odd x it should be 45=x*2+1 --> x=22=even, so not a valid solution.

Answer: D. ([88]=88/2+1=45).

Similar question to practice: for-all-positive-integers-m-3m-when-m-is-odd-and-123618.html

Hope it helps.
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galiya
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When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] 06 May 2012, 10:18
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thanks, Bunuel! i was hoping for such an easy explanation
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When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] 26 Jun 2012, 03:42
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Bunuel
was reviewing my posts and got a question (im pretty sure, after the explanation ill think- OMG it was so obvious, but anyway):
looking at the question above, why do we substitute [x], e.g. [7] or [4], instead of a and b?
x and a (or b) are not the same numbers.
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When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] 26 Jun 2012, 03:47
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Galiya
Bunuel
was reviewing my posts and got a question (im pretty sure, after the explanation ill think- OMG it was so obvious, but anyway):
looking at the question above, why do we substitute [x], e.g. [7] or [4], instead of a and b?
x and a (or b) are not the same numbers.
Show more

It should be: "When X is even, [x]=x/2+1, when X is odd [x]=2x+1 then [7]*[4]=?"
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galiya
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When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] 26 Jun 2012, 04:00
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+1 thank you for this and a lot of previous answers&explanations
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When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] 03 Nov 2014, 08:47
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Bunuel
Galiya
When X is even, [x]=a/2+1, when X is odd [x]=2a+1 then [7]*[4]=?

A. [22]
B. [44]
C. [45]
D. [88]
E. [90]

your thoughts?
i went with C and was happy till didn't see the official answer

[7]*[4]=(2*7+1)(4/2+1)=45.

Now, notice that the answer choices are also in boxes, so we have that [x]=45, which means that for even x it should be 45=x/2+1 --> x=88=even and for odd x it should be 45=x*2+1 --> x=22=even, so not a valid solution.

Answer: D. ([88]=88/2+1=45).

Similar question to practice: for-all-positive-integers-m-3m-when-m-is-odd-and-123618.html

Hope it helps.
Show more


Hi Bunuel,

Why do we not consider 22 as an answer? Is it because 22 as an answer was even when equated to an odd equation, i.e 2a+1? Does the solution also
have to be odd when equated to an odd equation (2a+1)?
I hope my question makes sense ... not sure if I was able to explain myself clearly? =P Please let me know!

Thanks as always!!
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When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] 03 Nov 2014, 08:58
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Rca
Bunuel
Galiya
When X is even, [x]=a/2+1, when X is odd [x]=2a+1 then [7]*[4]=?

A. [22]
B. [44]
C. [45]
D. [88]
E. [90]

your thoughts?
i went with C and was happy till didn't see the official answer

[7]*[4]=(2*7+1)(4/2+1)=45.

Now, notice that the answer choices are also in boxes, so we have that [x]=45, which means that for even x it should be 45=x/2+1 --> x=88=even and for odd x it should be 45=x*2+1 --> x=22=even, so not a valid solution.

Answer: D. ([88]=88/2+1=45).

Similar question to practice: for-all-positive-integers-m-3m-when-m-is-odd-and-123618.html

Hope it helps.


Hi Bunuel,

Why do we not consider 22 as an answer? Is it because 22 as an answer was even when equated to an odd equation, i.e 2a+1? Does the solution also
have to be odd when equated to an odd equation (2a+1)?
I hope my question makes sense ... not sure if I was able to explain myself clearly? =P Please let me know!

Thanks as always!!
Show more

We got that [7]*[4] = 45.

Now, [22], since 22 is even, is 22/2 + 1 = 12, not 45.

Does this make sense?
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When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] 11 Nov 2020, 07:40
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galiya
When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] = ?

A. [22]
B. [44]
C. [45]
D. [88]
E. [90]
Show more

(14+1)*[(4/2)+1]
15*3=45

Only [88/2]+1=45
Ans. D
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When x is even, [x] = x/2 + 1, when x is odd [x] = 2x + 1 then [7]*[4] 10 Oct 2025, 12:46
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