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Q:

Which of the following can be used to illustrate that not all prime numbers are odd?

A) 1	B) 2
C) 3	D) 4

Answer & Explanation Answer: B) 2

Explanation:

The only even numbers in the list are 2 and 4, but 4 is not a prime. So 2 can be used to illustrate the statement that all primes are not odd.

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Filed Under: Numbers
Exam Prep: GRE

Q:

Paint needs to be thinned to a ratio of 2 parts paint to 1.5 parts water. The painter has by mistake added water so that he has 6 litres of paint which is half water and half paint. What must he add to make the proportions of the mixture correct?

A) 1 litre paint	B) 1 litre water
C) ½ litre water and one litre paint	D) ½ litre paint and one litre water

Answer & Explanation Answer: A) 1 litre paint

Explanation:

At the moment the paint is 3 liters of paint and 3 liters of water. We need to add to this to make the new ratio 2 liters paint to 1.5 liters water. As this is equivalent to 4 : 3 we can see that we have the right amount of water, and just need 1 liter of paint to make it correct.

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Filed Under: Ratios and Proportions
Exam Prep: GRE

Q:

If a positive integer n, divided by 5 has a remainder 2, which of the following must be true?

A) n is odd	B) n + 1 cannot be a prime number
C) (n + 2) divided by 7 has remainder 2	D) n + 3 is divisible by 5

Answer & Explanation Answer: D) n + 3 is divisible by 5

Explanation:

You can find the integers which when divided by 5 have a remainder 2 by adding 2 to all multiples of 5. So we have n = 7 , 12, 17, 22 etc.

From this series we can see that n does not have to be odd.

Also n + 1 can be a prime because, for example, 12 + 1 = 13

And (n + 2) / 7 has a remainder 2 in some cases but not all.

Remember the question asks us for what MUST be true, and we see that none of the statements are true in all cases. However, adding 3 to any of the values of n will always give a multiple of 5.

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Filed Under: Numbers
Exam Prep: GRE

Q:

The volume of a rectangular solid is to be increased by 50% without altering its base. To what extent the height of the solid must be changed.

A) 50%	B) 40%
C) 30%	D) 20%

Answer & Explanation Answer: A) 50%

Explanation:

Let l, b the sides of the base, so that the area of the base = lb
remains constant.
Let ‘h’ be the height of the solid.
Volume of the solid, V = l× b× h.
Since the volume is to be increased by 50%

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Filed Under: Volume and Surface Area
Exam Prep: Bank Exams
Job Role: Bank PO

Q:

A cylindrical rod of iron, whose height is equal to its radius, is melted and cast into spherical balls whose radius is half the radius of the rod. Find the number of balls.

A) 3	B) 4
C) 5	D) 6

Answer & Explanation Answer: D) 6

Explanation:

Volume of rod = ${πr}^{2} h$ = ${πr}^{2} \times r$ = ${πr}^{3}$

Volume of one spherical ball =r/2

Volume of the spherical ball = $\frac{\frac{4}{3} {πr}^{3}}{8}$

Number of balls=Volumeof rod/volumeof one ball

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Filed Under: Volume and Surface Area
Exam Prep: Bank Exams
Job Role: Bank PO

Q:

If the radius of base and height of a cone are increased by 10%, find the percentage of increase of its volume

A) 33.5%	B) 33.1%
C) 32.1%	D) 53.1%

Answer & Explanation Answer: B) 33.1%

Explanation:

v1= $\frac{1}{3} {πr}_{1}^{2} h_{1}$

v2= $\frac{1}{3} {πr}_{2}^{2} h_{2}$

% Increase in volume = (V2-V1) / (V2*100)

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Filed Under: Volume and Surface Area
Exam Prep: Bank Exams
Job Role: Bank PO

Q:

Half the people on a bus get off at each stop after the first, and no one gets on after the first stop. If only one person gets off at stop number 7, how many people got on at the first stop?

A) 128	B) 64
C) 32	D) 16

Answer & Explanation Answer: B) 64

Explanation:

7th stop only one was left and in each preceding stop twice the nos... there were so 6 stops before 7th.

so $2^{6} = 64$

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Filed Under: Problems on Numbers
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 2 $n^{2}$ 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

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