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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:

An atom has 7 electrons in its M - shell and contains 18 neutrons in its nucleus. What is its mass number

A) 25 B) 27
C) 35 D) 43
 
Answer & Explanation Answer: C) 35

Explanation:

According to Bohr model, Each shell can occupy 2n2 electrons in their orbits where n=1,2,3.. for K,L,M,..

 

The atom has 2 electrons in k, 8 electrons in L and 7 electrons in M = 2 + 8 + 7 = 17

 

And given that its nucleus has 18 neutrons

 

=> its mass number = number of (electrons + neutrons ) = 17 + 18 = 35

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Filed Under: Chemistry

Q:

The atoms of the elements which have same number of neutrons are called

A) Isobars B) Isotopes
C) Isotones D) None
 
Answer & Explanation Answer: C) Isotones

Explanation:
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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:

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

Q:

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

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

Explanation:
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Q:

The distance from town A to town B is five miles. C is six miles from B. Which of the following could be the maximum distance from A to C? 

A) 11 B) 8
C) 2 D) 4
 
Answer & Explanation Answer: A) 11

Explanation:

Do not assume that AB and C are on a straight line. Make a diagram with A and B marked 5 miles apart. Draw a circle centered on B, with radius 6. C could be anywhere on this circle. The minimum distance will be 1, and maximum 11

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Filed Under: Time and Distance
Exam Prep: GRE