Friday, September 23, 2011

Challenge Yourself Question 2

[QUESTION]
The tens digit of a two-digit number is 5 more than the units digit. The number formed by reversing the digits is 128 less than twice the original number. Find the original number.

[EXPLANATION]
To get the Original Number:
Need to have 'x' tens and 'y' ones
-> 10x + y
(Try replacing 'x' with any value to understand the need for the 10 times- as this is addition)
eg. x=7 , y=8
so to get 78, you will have to have 10(7) + 8 as it is 7 TENS and 8 ONES

To get Reversed Number:
Need to have 'y' tens and 'x' ones
-> 10y + x

[ANALYZATION]
The tens digit of a two-digit number is 5 more than the units digit : (Original Number)
-> x = y + 5

The number formed by reversing the digits is 128 less than twice the original number :
-> 10y + x = 2(10x + y) - 128
( from here, set up the equation )

3 comments:

  1. Well done Valery, clear explanation and easy to understand.

    ReplyDelete
  2. Sylvia Soh- S1099/28/2011 10:38:00 AM

    Very clear and quite easy to understand. Pencil line could be darker though :)

    ReplyDelete