The sum of digits of a two digit number is 15. The number obtained by interchanging the digits exceeds the given number by 9. The number is.
Explanation
Step 1: Set up the first equation (Sum of digits)
The sum of the digits is 15:
x+y=15— (Equation 1)
Step 2: Set up the second equation (Interchanging digits)
The number obtained by interchanging the digits exceeds the original number by 9:
Reversed Number−Original Number=9
(10y+x)−(10x+y)=9
Simplify the expression:
10y+x−10x−y=9
9y−9x=9
Divide the entire equation by 9:
y−x=1
−x+y=1— (Equation 2)
Step 3: Solve the system of linear equations
Add Equation 1 and Equation 2:
(x+y)+(−x+y)=15+1
2y=16
y=216
y=8
Substitute y=8 back into Equation 1:
x+8=15
x=15−8
x=7
Step 4: Form the original number
Substitute the values of tens digit (x=7) and units digit (y=8) into the original number form:
Original Number=10x+y=10(7)+8=78