Aptitude - Numbers

2, 6, 12, 20, 30, 42, 56, (__)

A.  60

B.  64

C.  72

D.  70

View Answer  

Correct Answer :

72



Explanation :

The sequence is 1 * 2, 2 * 3, 3 * 4, 4 * 5, 5 * 6, 6 * 7, 7 * 8.
.'. Missing number = 8 * 9 = 72.


Let N = 553 + 173 - 723. N is divisible by:

A.  both 7 and 13

B.  both 3 and 13

C.  both 17 and 7

D.  both 3 and 17

View Answer  

Correct Answer :

both 3 and 17



Explanation :
No Explanation available for this question

6, 12, 48, 100, 384, 768, 3072 Find out the wrong number in the series.

A.  768

B.  100

C.  384

D.  12

E.  48

View Answer  

Correct Answer :

100



Explanation :

Each even term of the series is obtained by multiplying the previous term by 2.

2nd term = (1st term) x 2 = 6 x 2 = 12

4th term = (3rd term) x 2 = 48 x 2 = 96.

6th term = (5th term) x 2 = 384 x 2 =768.

 4th term should be 96 instead of 100.


40.83 x 1.02 x 1.2 =?

A.  41.64660

B.  49.97592

C.  42.479532

D.  58.7952

View Answer  

Correct Answer :

49.97592



Explanation :

4083 X 102 X 12 = 4997592. Sum of decimal places = 5.

∴ 40.83 X 1.02 X 1.2 = 49.97592.

 


The H.C.F. of 2923 and 3239 is :

A.  37

B.  47

C.  73

D.  79

View Answer  

Correct Answer :

79



Explanation :

The HCF will be 79 for both as follows
2923 ) 3239 ( 1
       -  2923 
            316 ) 2923 ( 9
                 -  2844
                        79 ) 316 ( 4
                            - 316
                                X


The value of (4.7 x13.26 + 4.7 x 9.43 + 4.7 x 77.31 ) is

A.  0.47

B.  47

C.  470

D.  4700

View Answer  

Correct Answer :

470



Explanation :

(4.7 x 13.26 + 4.7 x 9.43 + 4.7 x 77.31)
= 4.7 (13.26 + 9.43 + 77.31)
= 4.7 x 100
= 470


Given that 268*74 =19832, find the values of 2.68 * 0.74.

A.  1.9832

B.  1.9831

C.  1.8831

D.  1.9952

View Answer  

Correct Answer :

1.9832



Explanation :

Sum of decimal places = (2 + 2) = 4
2.68 * 0.74 = 1.9832.


How many factors of 25*36*52 are perfect squares?

A.  20

B.  24

C.  26

D.  28

View Answer  

Correct Answer :

24



Explanation :

Any factor of this number should be of the form 2a×3b×5c.

For the factor to be a perfect square a, b, c have to be even.
a can take values 0, 2, 4. b can take values 0,2, 4, 6 and c can take values 0,2.

Total number of perfect squares =3×4×2= 24


H.C.F. of 3240, 3600 and a third number is 36 and their L.C.M. is 2^4 x 3^5 x 5^2 x 7^2 The third number is:

A.  2^2 x 3^5 x 7^2

B.  2^2 * 5^3 * 7^2

C.  2^2 * 5^2 * 7^2

D.  2^3 * 3^5 * 7^2

View Answer  

Correct Answer :

2^2 x 3^5 x 7^2



Explanation :

3240 = 2^3 x 3^4 x 5; 3600 = 2^4 x 3^2 x 5^2; H.C.F. = 36 = 2^2 x 3^2 Since H.C.F. is the product of lowest powers of common factors, so the third number must have (2^2 x 3^2) as its factors Since L.C.M. is the product of highest powers of common prime factors, so the third number must have 3^5 and 7^2 as its factors. Third number = 2^2 x 3^5 x 7^2


If n is a natural number, then (6n2 + 6n) is always divisible by:

A.  6 only

B.  12 only

C.  6 and 12 both

D.  by 18 only

View Answer  

Correct Answer :

6 and 12 both



Explanation :

(6n2 + 6n) = 6n(n + 1), which is always divisible by 6 and 12 both, since n(n + 1) is always even.


An automobile financier claims to be lending money at simple interest, but he includes the interest every six months for calculating the principal. If he is charging an interest of 10%, the effective rate of interest becomes:

A.  10%

B.  10.25%

C.  10.5%

D.  None of these

View Answer  

Correct Answer :

10.25%



Explanation :

Let the sum be Rs. 100. Then,

 

S.I. for first 6 months = Rs. 100 x 10 x 1 = Rs. 5
100 x 2

 

 

S.I. for last 6 months = Rs. 105 x 10 x 1 = Rs. 5.25
100 x 2

 

So, amount at the end of 1 year = Rs. (100 + 5 + 5.25) = Rs. 110.25

i.e Effective rate = (110.25 - 100) = 10.25%