| json_metadata | "{"app":"Musing","appTags":["maths"],"appCategory":"maths","appTitle":"How many four digit numbers can be formed using every digit only once in the number?","appBody":"<p><strong>Using a very short cut</strong></p>\n<p>We have natural digit from 0-9</p>\n<p>If we have to form a four digit number from then:</p>\n<p><strong>For the first digit;</strong></p>\n<p>There are 10 different numbers which can occupy the first digit, i.e(0,1,2,3,4,5,6,7,8,9)</p>\n<p><strong>For the 2nd digit;</strong></p>\n<p>There would be 9 digit remaining to be selected if one have been previous selected for first digit.</p>\n<p><strong>For the 3rd digit;</strong></p>\n<p>There would be 8 digit remaining to be selected if two had already be selected for 1st and 2nd digit.</p>\n<p><strong>For the 4th digit;</strong></p>\n<p>There would be 7 digit remaining to be selected since three had been selected for 1st, 2nd and 3rd digit.</p>\n<p>Then the number of the digit numbers that can be formed will be the product of the number of selectable digits. That is;</p>\n<p><strong>10 × 9 × 8 ×7 = 5,040</strong> number</p>\n<p><br></p>\n<p>I hope that is helpful...</p>","appDepth":2,"appParentPermlink":"p3enxvznx","appParentAuthor":"vedvati","musingAppId":"aU2p3C3a8N","musingAppVersion":"1.1","musingPostType":"answer"}" |
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