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Question
How many numbers greater than 200 and divisible by 2 can be made from the digits 4, 5, 6, and 7 if no digit is repeated.
Options
6
12
24
30
MCQ
Fill in the Blanks
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Solution
12
Explanation:
Numbers that are divisible by 2 must have '4' fixed in the extreme right place
| 3 Digit Numbers | 4 Digit Numbers | |||||
| H | T | U | Th | H | T | U |
| × | × | 4 | × | × | × | 4 |
| `""^3"P"_2` ways = `(3!)/(1!) = 3 xx 2 = 6` |
`""^3"P"_3` ways = `(3!)/(0!) = 3 xx 2 = 6` |
|||||
⇒ Total ways = 6 + 6 = 12
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Invariance Principle
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