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GATE 2020 EE – Question 8

General Aptitude · Quantitative Aptitude: Probability and Combinatorics · 2 marks · Multiple choice

In four-digit integer numbers from 1001 to 9999, the digit group "37" (in the same sequence) appears ________ times.

  1. 270
  2. 279
  3. 280
  4. 299

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Correct answer: (C) 280

Explanation

Count by the position of "37". In digits 1-2 there are $100$ numbers (37xx). In digits 2-3 the first digit is 1 to 9 and the last is any of 10, giving $90$. In digits 3-4 there are $9\times10=90$. The total is $100+90+90=280$.