Number System-Railway Maths

Total Questions: 50

31. X attempts 94 questions and gets 141 marks. If for every correct answer 4 marks is given, and for every wrong answer 1 mark is deducted, then the number of questions wrongly answered by X is_____________. [RRB ALP Tier - 1 17/08/2018 (Morning)]

Correct Answer: (c) 47
Solution:Here, 1 + 1 = 2 unit = 94 questions
Then, 1 unit = 94/2 = 47
The no of question wrongly answered by x = 47

32. Which of the following is divisible by both 4 and 8? [Group D 17/08/2022 (Afternoon)]

Correct Answer: (c) 3824
Solution:

Divisibility of 4 digits = last two digit must be divisible by 4.
Divisibility of 8 = last three digits must be divisible by 8.
Here, 3824 is divisible by both 4 and 8.

33. Find the number of 2-digit numbers divisible by both 2 and 4. [Group D 17/08/2022 (Evening)]

Correct Answer: (c) 22
Solution:

34. If x and y are the two digits of the number 115 xy such that this number is divisible by 90, then the value of x + y is: [Group D 18/08/2022 (Afternoon)]

Correct Answer: (b) 2

35. The smallest natural number that must be added to 1212 to make it a perfect square is: [Group D 18/08/2022 (Afternoon)]

Correct Answer: (a) 13
Solution:

34² < 1212 < 35²
Smallest number that should be added
= 35² - 1212 = 1225 - 1212 = 13

36. Which of the following pairs of numbers are co - primes? [Group D 18/08/2022 (Afternoon)]

Correct Answer: (a) 34 and 35
Solution:

HCF of coprime number = 1.
H.C.F of 34 and 35 = 1.

37. Find the smallest number by which 6300 must be multiplied to make it a perfect square. [Group D 18/08/2022 (Afternoon)]

Correct Answer: (d) 7
Solution:

6300 = 2 × 2 × 3 × 3 × 5 × 5 × 7
Hence, 7 must be multiplied by 6300 to make a perfect square.
6300 × 7 = 44100 = 210²

38. The sum of two numbers is 32 and one of them exceeds the other by 18. Find the greater number. [Group D 18/08/2022 (Evening)]

Correct Answer: (b) 25
Solution:

Let the number are x and x + 18.
Now, x + x + 18 = 32
⇒ 2x = 32 - 18 ⇒ 2x = 14 ⇒ x = 7
Greater number = x + 18 = 7 + 18 + 25

39. Which of the following pairs is NOT coprime? [Group D 18/08/2022 (Evening)]

Correct Answer: (d) (17, 34)
Solution:

(11, 13) is co-prime because H.C.F of 11 and 13 = 1
(15, 17) is co-prime because H.C.F of 15 and 17 = 1
(17, 23) is co-prime because H.C.F of 17 and 23 = 1
(17, 34) is not co-prime because H.C.F of 17 and 34 = 17

40. Mohit's salary is ₹15,000 per month. He spends ₹5,000 on house rent. 2000 on bills and rest of the amount is his monthly savings. Find his savings in a year, if in the month of his birthday he spent his complete monthly saving for birthday celebration. [Group D 18/08/2022 (Evening)]

Correct Answer: (a) ₹88,000
Solution:

Mohit's 1 month salary= ₹15000
His 1 month expenditure = 5000 + 2000 = ₹7000
1 month saving = 15000-7000 = ₹8000
He spends his total saving of birthday month on celebration.
Now, his saving for 11 month = 8000 × 11 = ₹ 88,000