1. Write all possible numbers using the digits 3,6 and 8 without repeating of digits. Solution: The numbers are: 3 at unit place: 863 ,683 Hint: keep 3 at unit place and interchange the position of 8 and 6 6 at unit place: 836 , 386 Hint: keep 6 at unit place and interchange the position of 8 and 3 8 at unit place: 638 ,368 Hint: keep 8 at unit place and interchange the position of 6 and 3 Question: Do it yourself for 2,4 and 9 2. How many whole numbers have two digits. Solution: The two digits whole numbers are from 10 to 99. e.g. 10,11,12......99. Therefore the two digit numbers= 99-(10-1) =99-9 =90 Note: Its general formula is : For two digits number = two digits highest number-(two digits lowest number-1) 3. How many whole numbers have three digits. Solution: The two digits whole numbers are from 100 to 999. e.g. 100,101,102......999. We will apply the same formula by changing the numbers of digits only. Therefore the three di