# RRB NTPC - Number System : Aptitude Test (200 Questions with Explanation)

41.

68n - 58n, where n>0 is an integer, is divisible by

A.) 6
B.) 671
C.) 21
D.) 39

For n = 1,
68 - 5 8 = (64)2 - (54)2 = (64 + 54)(64 - 54)
= (1921) (671)

42.

6/7 of a certain number is 96. Find quarter of that number.

A.) 112
B.) 23
C.) 32
D.) 28

6/7x = 96
x = 112
y = x/4 = 112/4 = 28

43.

Find the HCF of 59 , 14?

A.) 826
B.) 1
C.) 2
D.) 3

The fastest way to find the correct answer is by elimination rule :
Check whether each of the given choices divides both the numbers. If any of the given choices doesnâ€™t divide both the numbers, then you can eliminate that particular choice and move to the next choice. Answer will be the HIGHEST Number that exactly divides both given numbers.
Please Note : There may be a scenario when two or more numbers in the choice will exactly divide both the numbers, in that case , please choose the Highest among the numbers.

44.

Two people run around circular track and take 42 sec and 30 sec to make one complete round. If they start together after how much amount of time will they meet again in the same place?

A.) 3 min 30 sec
B.) 4 min 40 sec
C.) 3 min 20 sec
D.) 2 min 50 sec

LCM ( 42, 30) = 210
They will meet in 210 seconds, which is 3 min 30 sec.

45.

What number should come next ?
173, 196, 219, 242, _____

A.) 265
B.) 267
C.) 263
D.) 264

The given series is -- 173, 196, 219, 242
Consequtive numbers increases by 23
Following this pattern, the Missing Number should increase by 23 from the previous number.
When we add 23 to the last number (i.e 242) we get 242+23=265

46.

What should come in place of _____ in the below number series?
173, 149, 125, 101, _____

A.) 76
B.) 77
C.) 78
D.) 79

The given series is -- 173, 149, 125, 101
Consequtive numbers decreases by 24
Following this pattern, the Missing Number should decrease by 24 from the previous number.
When we subract 24 to the last number (i.e 101) we get 101- 24 = 77

47.

Find the HCF of 59 , 12?

A.) 1
B.) 2
C.) 3
D.) 708

The fastest way to find the correct answer is by elimination rule :
Check whether each of the given choices divides both the numbers. If any of the given choices doesnâ€™t divide both the numbers, then you can eliminate that particular choice and move to the next choice. Answer will be the HIGHEST Number that exactly divides both given numbers.
Please Note : There may be a scenario when two or more numbers in the choice will exactly divide both the numbers, in that case , please choose the Highest among the numbers.

48.

Find the LCM of 42 , 20?

A.) 504
B.) 360
C.) 1680
D.) 420

The fastest way to find the correct answer is by elimination rule :
Check whether each of the given choices is divisble by both the numbers. If any choice doesnâ€™t get divided by both the numbers, then you can eliminate that particular choice and move to the next number. Answer will be the Number that is exactly divisble by both given numbers.
Please Note : There may be a scenario when two or more numbers in the choice will be exactly divisible by both the numbers, in that case , please choose the lowest among the numbers.

49.

In the below given sequence, what should be the next number?
173, 195, 217, 239, _____

A.) 263
B.) 261
C.) 259
D.) 260

The given series is -- 173, 195, 217, 239
Consequtive numbers increases by 22
Following this pattern, the Missing Number should increase by 22 from the previous number.
When we add 22 to the last number (i.e 239) we get 239+22=261

50.

Output of a particular program follows the below pattern. Can you find the next number ?
173, 151, 129, 107, _____

A.) 84
B.) 83
C.) 87
D.) 85

The given series is -- 173, 151, 129, 107
Consequtive numbers decreases by 22
Following this pattern, the Missing Number should decrease by 22 from the previous number.
When we subract 22 to the last number (i.e 107) we get 107-22 = 85

51.

Find the HCF of 59 , 10?

A.) 1
B.) 2
C.) 3
D.) 590

The fastest way to find the correct answer is by elimination rule :
Check whether each of the given choices divides both the numbers. If any of the given choices doesnâ€™t divide both the numbers, then you can eliminate that particular choice and move to the next choice. Answer will be the HIGHEST Number that exactly divides both given numbers.
Please Note : There may be a scenario when two or more numbers in the choice will exactly divide both the numbers, in that case , please choose the Highest among the numbers.

52.

Two bells toll at an interval of 42 and 24 seconds respectively. After they start at the same time, again after how many seconds will they rings together?

A.) 420
B.) 432
C.) 504
D.) 168

The fastest way to find the correct answer is by elimination rule :
Check whether each of the given choices is divisble by both the numbers. If any choice doesnt get divided by both the numbers, then you can eliminate that particular choice and move to the next number. Answer will be the Number that is exactly divisble by both given numbers.
Please Note : There may be a scenario when two or more numbers in the choice will be exactly divisible by both the numbers, in that case , please choose the lowest among the numbers.

53.

Fifth number is missing in the below series. Can you find the fifth number in the below series ?
173, 190, 207, 224, _____

A.) 241
B.) 239
C.) 243
D.) 240

The given series is -- 173, 190, 207, 224
Consequtive numbers increases by 17
Following this pattern, the Missing Number should increase by 17 from the previous number.
When we add 17 to the last number (i.e 224) we get 224+17=241

54.

Find the HCF of 59 , 22?

A.) 1
B.) 2
C.) 3
D.) 1298

The fastest way to find the correct answer is by elimination rule :
Check whether each of the given choices divides both the numbers. If any of the given choices doesnâ€™t divide both the numbers, then you can eliminate that particular choice and move to the next choice. Answer will be the HIGHEST Number that exactly divides both given numbers.
Please Note : There may be a scenario when two or more numbers in the choice will exactly divide both the numbers, in that case , please choose the Highest among the numbers.

55.

Find the LCM of 42 , 3?

A.) 54
B.) 42
C.) 84
D.) 168

The fastest way to find the correct answer is by elimination rule :
Check whether each of the given choices is divisble by both the numbers. If any choice doesnâ€™t get divided by both the numbers, then you can eliminate that particular choice and move to the next number. Answer will be the Number that is exactly divisble by both given numbers.
Please Note : There may be a scenario when two or more numbers in the choice will be exactly divisible by both the numbers, in that case , please choose the lowest among the numbers.

56.

What should come in place of X in the below number series?
117, 88, 59, X , 1, -28

A.) 29
B.) 28
C.) 32
D.) 30

The given series is 117, 88, 59, X , 1, -28
Consequtive numbers decreases by 29
Following this pattern, the Missing Number X should decrease by 29 from the previous number.
When we subract 29 to the number before X (i.e 59) we get 59 - 29 = 30

57.

Output of a particular program follows the below pattern. Can you find the Missing number?
117, 146, 175, X , 233, 262

A.) 203
B.) 202
C.) 206
D.) 204

The given series is -- 117, 146, 175, X , 233, 262
Consequtive numbers increases by 29
Following this pattern, the Missing Number X should increase by 29 from the previous number.
When we add 29 to the number before X (i.e 175) we get 175+29=204

58.

Find the LCM of 25 , 3?

A.) 75
B.) 150
C.) 48
D.) 100

The fastest way to find the correct answer is by elimination rule :
Check whether each of the given choices is divisble by both the numbers. If any choice doesnâ€™t get divided by both the numbers, then you can eliminate that particular choice and move to the next number. Answer will be the Number that is exactly divisble by both given numbers.
Please Note : There may be a scenario when two or more numbers in the choice will be exactly divisible by both the numbers, in that case , please choose the lowest among the numbers.

59.

Find the HCF of 12 , 22?

A.) 1
B.) 2
C.) 4
D.) 132

The fastest way to find the correct answer is by elimination rule :
Check whether each of the given choices divides both the numbers. If any of the given choices doesnâ€™t divide both the numbers, then you can eliminate that particular choice and move to the next choice. Answer will be the HIGHEST Number that exactly divides both given numbers.
Please Note : There may be a scenario when two or more numbers in the choice will exactly divide both the numbers, in that case , please choose the Highest among the numbers.

60.

Find the HCF of 12 , 6?

A.) 1
B.) 2
C.) 6
D.) 12