In a two digit number,the unit's digit is 7 more than the ten's digit. sum of the digits is 1/2 of the whole number. find the digits and number
Answers
Because the units digit is 7 more than the ten's, it cannot be 0, 1, 2, 3, 4, 5 or 6 because they are to small. Similarly, the tens digits cannot be 4, 5, 6, 7, 8, or 9 (we will just say that the number does not start with a 0 as a general rule)
This leaves us with only a couple of numbers to work with, which is good. Numbers such as 17 18 19 27 28 29 37 38 39 (a very small amount).
From here we go practical and add the digits together. 8 9 10 9 10 11 10 11 12. As we can see that the numbers only range from 8 to 12, we can safely get rid of extremely small and large numbers such as 17 39 38 37 29 28 27.
Leaving us with only 18 and 19; and their corresponding numbers of 9 and 10.
I hope you can see the answer from here and I hope this helps XD