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GATE 2019 EE – Question 6

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

How many integers are there between 100 and 1000 all of whose digits are even?

  1. 60
  2. 80
  3. 100
  4. 90

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Show answer and explanation

Correct answer: (C) 100

Explanation

The hundreds digit can be 2, 4, 6 or 8 (4 choices, not 0), and the tens and units digits can each be 0, 2, 4, 6 or 8 (5 choices each). The count is $4\times5\times5=100$.