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Q:

A perfect cube is an integer whose cube root is an integer. For example, 27, 64 and 125 are perfect cubes. If p and q are perfect cubes, which of the following will not necessarily be a perfect cube?

A) 8p B) pq
C) pq+27 D) -p
 
Answer & Explanation Answer: C) pq+27

Explanation:

A perfect cube will have prime factors that are in groups of 3; for example 125 has the prime factors 5 x 5 x 5 , and 64 x 125 will also be a cube because its factors will be 4 x 4 x 4 x 5 x 5 x 5

Consider the answer choices in turn.

8 is the cube of 2, and p is a cube, and so the product will also be a cube.

pq will also be a cube as shown above.

pq is a cube and so is 27, but their sum need not be a cube. Consider the case where p =1 and q = 8, the sum of pq and 27 will be 35 which has factors 5 x 7 and is not a cube.

-p will be a cube.

Since the difference between p and q is raised to the power of 6, this expression will be a cube (with cube root = difference squared).

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Filed Under: Numbers

Q:

One side of a triangle has length 8 and a second side has length 5. Which of the following could be the area of the triangle?

A) 24 B) 20
C) 26 D) 34
 
Answer & Explanation Answer: B) 20

Explanation:

The maximum area of the triangle will come when the given sides are placed at right angles. If we take 8 as the base and 5 as the height the area = ½ x 8 x 5=20

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Filed Under: Volume and Surface Area
Exam Prep: GRE

Q:

 If n is even, which of the following cannot be odd?

A) n+3 B) 2n
C) n+4 D) 3n
 
Answer & Explanation Answer: B) 2n

Explanation:

In case B, odd times even will give even

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Filed Under: Numbers
Exam Prep: GRE

Q:

The atoms of the elements having same atomic number but different mass number are called

A) Isobar B) Isotopes
C) Iso electronic D) Isotones
 
Answer & Explanation Answer: B) Isotopes

Explanation:
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Filed Under: Chemistry

Q:

-20 , -16 , -12 , -8 .... 

In the sequence above, each term after the first is 4 greater than the preceding term. Which of the following could not be a term in the sequence? 

A) 220 B) 440
C) 668 D) 762
 
Answer & Explanation Answer: D) 762

Explanation:

All terms in the sequence will be multiples of 4.

762 and 902 are not multiples of 4

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Filed Under: Sequential Output Tracing
Exam Prep: GRE

Q:

Two boys starting from the same place walk at a rate of 5kmph and 5.5kmph respectively. What time will they take to be 8.5km apart, if they walk in the same direction?

A) 15 hours B) 16 hours
C) 17 hours D) 18 hours
 
Answer & Explanation Answer: C) 17 hours

Explanation:

In this type of questions we need to get the relative speed between them,
The relative speed of the boys = 5.5kmph – 5kmph
= 0.5 kmph

Distance between them is 8.5 km
Time = Distance/Speed
Time= 8.5km / 0.5 kmph = 17 hrs

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Filed Under: Time and Distance
Exam Prep: GRE

Q:

Species containing same number of electrons are called

A) Isotopes B) Isobars
C) Isoelectronic D) Isotones
 
Answer & Explanation Answer: C) Isoelectronic

Explanation:
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Filed Under: Chemistry

Q:

A man in a train notices that he can count 41 telephone posts in one minute. If they are known to be 50 metres apart, then at what speed is the train travelling?

A) 60 km/hr B) 100 km/hr
C) 110 km/hr D) 120 km/hr
 
Answer & Explanation Answer: D) 120 km/hr

Explanation:

Number of gaps between 41 poles = 40
So total distance between 41 poles = 40*50
= 2000 meter = 2 km
In 1 minute train is moving 2 km/minute.
Speed in hour = 2*60 = 120 km/hour

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Filed Under: Time and Distance
Exam Prep: GRE