Question

a two digit number is 7 times the sum of its digit. if the difference between two digit is 2,find the number

Answer 1

Let one digit be x
Other is y

Therefore
10y + x = 7x + 7y -- (1)

y-x=2
y = x+ 2 --(2)


Comparing 1 and 2

3y - 6x = 0
3(x+2) -6x = 0
3x + 6 -6x = 0
-3x = -6
x = 2

Therefore y = 4

Hence the number is 42.

Answer 2

Let the two digit number be 10X+Y
Then 10X+Y=7(X+Y)
:- 3x-6y=0
since,x=y+2
3(y+2)-6y=0
3y=6
y=2
x=4
two digit number is 42