Quantitative Aptitude - Arithmetic Ability Questions

Q:

What is the number of digits in 333? Given that log3 = 0.47712?

A) 12 B) 13
C) 14 D) 15
 
Answer & Explanation Answer: B) 13

Explanation:

 Let   Let x=333 333

 

 Then, logx = 33 log3  

 

= 27 x 0.47712 = 12.88224 

 

Since the characteristic in the resultant value of log x is 12

 

The number of digits in x is (12 + 1) = 13 

 

Hence the required number of digits in 333is 13.

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Filed Under: Logarithms
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Q:

There are 2 brothers among a group of 20 persons. In how many ways can the group be arranged around a circle so that there is exactly one person between the two brothers?

A) 18! x 19! B) 2 x 19!
C) 2 x 18! D) 18! x 18!
 
Answer & Explanation Answer: C) 2 x 18!

Explanation:

fix one person and the brothers B1 P B2 = 2 ways to do so.
other 17 people= 17!

 
Each person out of 18 can be fixed between the two=18, thus, 2 x 17! x 18=2 x 18!

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Q:

Find the one which does not belong to that group ?

A) 343 B) 2197
C) 1331 D) 121
 
Answer & Explanation Answer: D) 121

Explanation:

343 = 73,  1331 = 113 , 2197 = 133, 121 = 112

 

343, 1331, 2197 are perfect cubes, but not 121.

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Filed Under: Odd Man Out
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12 12158
Q:

How many  18' s are there in  3712?

A) 300 B) 400
C) 500 D) 600
 
Answer & Explanation Answer: A) 300

Explanation:

3712 = 752

Required number =  75218 = 75 x 4 = 300

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Filed Under: Simplification
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23 12119
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

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Q:

Two numbers are in the ratio 3 : 7. If 6 be added to each of them, then they are in the ratio 5 : 9. Find the numbers ?

A) 11 & 17 B) 7 & 17
C) 9 & 21 D) 13 & 23
 
Answer & Explanation Answer: C) 9 & 21

Explanation:

Let the two numbers be x and y

Given x : y = 3 : 7 .....(1)

Now, x+6 : y+6 = 5 : 9 .....(2)

From (1), x = 3y/7

From (2), 5y - 9x = 24

=> 5y - 9(3y/7) = 24

=> y = 21

=> From(1), x = 9

Hence, the two numbers be 9 and 21

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Filed Under: Ratios and Proportions
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Q:

Find x if 

log1218 = log24x + 1. log24x+1 + 4

A) 0 B) 1
C) 2 D) None of these
 
Answer & Explanation Answer: A) 0

Explanation:

By trial and error method, when we substitute 

x = 0

Both LHS and RHS are equal.

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Filed Under: Logarithms
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24 12106
Q:

In what time will Rs. 1860 amount to Rs. 2641.20 at simple interest 12% per annum?

A) 2.9 years B) 3.5 years
C) 4.2 years D) 4.7 years
 
Answer & Explanation Answer: B) 3.5 years

Explanation:

Given that Rs. 1860 will become Rs. 2641.20 at 12%

 

=> Simple Interest = 2641.20 - 1860 = Rs. 781.20

 

We know I = PTR/100

 

=> 781.20 x 100 = 1860 x T x 12

 

=> T = 78120/1860x12

 

=> T = 78120/22320

 

=> T = 3.5 years.

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Filed Under: Simple Interest
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