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RRB NTPC Number System — practice questions — page 3

Explore 64 free Number System questions in RRB NTPC Quantitative Aptitude. Open each question or exercise to read its content, reference answers and available explanation.

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Number System questions and exercises with answers

Showing questions 61–64 of 64.

Under the ancient rules formulated by Brahmagupta, subtracting zero from a fortune results in what?Read the answer and worked solution →If the 7-digit number 5432y71 is divisible by 9, what is the single-digit value of y?Read the answer and worked solution →The fundamental theorem of arithmetic guarantees that prime factorization of an integer is unique apart from:Read the answer and worked solution →For rational numbers a/b and c/d with strictly positive denominators, a/b < c/d holds precisely when:Read the answer and worked solution →

Worked practice questions

Under the ancient rules formulated by Brahmagupta, subtracting zero from a fortune results in what?

  1. A zero quantity
  2. A negative debt
  3. An undefined value
  4. The same fortune
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Correct answer: D. The same fortune

Subtracting zero from any asset leaves the fortune unchanged.

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If the 7-digit number 5432y71 is divisible by 9, what is the single-digit value of y?

  1. 5
  2. 6
  3. 7
  4. 4
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Correct answer: A. 5

A number is divisible by 9 if and only if the sum of its digits is divisible by 9. Sum of digits = 5 + 4 + 3 + 2 + y + 7 + 1 = 22 + y. For 22 + y to be divisible by 9, the nearest multiple of 9 greater than or equal to 22 is 27. 22 + y = 27 => y = 5. Since y is a single digit (0 <= y <= 9), y = 5 is the unique valid value.

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The fundamental theorem of arithmetic guarantees that prime factorization of an integer is unique apart from:

  1. the signs of factors
  2. the order of factors
  3. the number of digits
  4. the base of notation
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Correct answer: B. the order of factors

The prime factors of any positive integer are completely unique except for their order.

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