# Engineering Maths - Combinatories

>>>>>>>>Combinatories

• Option : B
• Explanation : n = 26 x 25 x 10 x 9 x 8=468000. i.e. there are twenty-six choices for the first letter, but only twenty-five choices for the second letter which must be different from the first letter. Similarly, choices for the digits are 10, 9 and 8 since the digits must be distinct.

• Option : C
• Explanation : Each letter can be printed in twenty-six different ways, the first digit in nine ways and each of the other two digits in ten ways. Hence 26 x 26 x 9 x 10 x 10 = 608400 different plates can be printed.

Common data  for next 2 questions

Given : npr = 3024.

• Option : D
• Explanation : Since np is product of consecutive positive integers, npr=3024=9x8x7x6 Hence n=9 and r = 4

• Option : B
• Explanation : Since np is product of consecutive positive integers, npr=3024=9x8x7x6 Hence n=9 and r = 4
Related Quiz.
Combinatories