6 positive integers are taken at random and multiplied together - Wikitechy https://www.wikitechy.com/interview-questions/tag/6-positive-integers-are-taken-at-random-and-multiplied-together/ Interview Questions Mon, 06 Sep 2021 05:48:02 +0000 en-US hourly 1 https://wordpress.org/?v=6.9 https://www.wikitechy.com/interview-questions/wp-content/uploads/2025/10/cropped-wikitechy-icon-32x32.png 6 positive integers are taken at random and multiplied together - Wikitechy https://www.wikitechy.com/interview-questions/tag/6-positive-integers-are-taken-at-random-and-multiplied-together/ 32 32 Four whole number taken at random are multiplied together. The chance that the last digit of the product is 1, 3, 7, or 9 is ? https://www.wikitechy.com/interview-questions/probability/four-whole-number-taken-at-random-are-multiplied-together-the-chance-that-the-last-digit-of-the-product-is-1-3-7-or-9-is/ https://www.wikitechy.com/interview-questions/probability/four-whole-number-taken-at-random-are-multiplied-together-the-chance-that-the-last-digit-of-the-product-is-1-3-7-or-9-is/#respond Wed, 18 Aug 2021 02:12:01 +0000 https://www.wikitechy.com/interview-questions/?p=2052

Four whole number taken at random are multiplied together. The chance that the last digit of the product is 1, 3, 7, or 9 is ?

A. 16/625

B. 1/210

C. 8/125

D. 4/25

Answer : A. 16/625

Explanation:

  • Since the product has to end in 1, 3, 7 or 9, the units place of all the 4 numbers we want to multiply can’t end in 0, 2, 4, 5, 6, 8. That means it can only end in 1, 3, 7, 9.
  • This means that the probability of selecting one number that ends in 1, 3, 7 or 9 is 4/10 = 2/5.
  • Therefore the probability of selecting four numbers that end in 1, 3, 7 or 9 is (2/5) x (2/5) x (2/5) x (2/5) = 16/625.
  • Hence, the probability of selecting 4 numbers such that their product ends in 1, 3, 7 or 9 is 16/625.
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