Question

how many 4 digit number can be formed using the digits 9,8,7,6,5,4 if no digits are repeated​

Answer 1

Answer:

7777 are not repeating digit

Answer 2

Given :- How many 4 digit number can be formed using the digits 9,8,7,6,5,4 if no digits are repeated ?

Answer :-

→ Total number of digits = 9,8,7,6,5,4 = six .

since no number is repeated .

• Any number from 6 comes at first place .
• Any number from rest 5 comes at second place .

then,

→ Total number of possibilities are = 6(C)4 = 6!/(4! * 2!) = 6 * 5 / 2 = 15 .

and,

→ 4 digits numbers can be arranged in = 4! = 4 * 3 * 2 = 24 ways .

therefore,

→ Total number of ways = 15 * 24 = 360 (Ans.)

[ shortcut :- 6(p)4 = 6! / 2! = 6 * 5 * 4 * 3 = 360 ways. ]

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