Answer:
Original number is 52.
Step-by-step explanation:
1) Two digit number xy,
it can be written as 10x + y.
2) The sum of the digits of a two-digit number is 7.
x + y = 7
3) The digits are interchanged the reversed number is yx,
the new number can be written as 10y + x.
4) The original number is 10x + y, so the tens digit of the original number is x.
5) Five times the tens digit of the original number is 5*x.
6) The reversed number is five times the tens digit of the original number:
10y + x = 5*x
7) We have system of two equations
x + y = 7 ----> x = 7 - y
10y + x = 5*x ---> 10y - 4x = 0
10y - 4x = 0
10y - 4(7 - y) =0
10y - 28 + 4y = 0
14y = 28
y = 2
x = 7 - y = 7 - 2 = 5
x = 5
Original number is 52.
New number 25.
Check:
Original number is 52, the tens digit is 5.
The reversed number (25) is five times the tens digit of the original number find the original number .
25 = 5*5 True
