Question

Question : what is the two-digit number? i. sum of the digits is 7. ii. difference between the number and the number obtained by interchanging the digits is 9. iii. digit in the ten's place is bigger than the digit in the unit's place by 1.

Answer 1

Hii friend ,

Solution :-

Let the ten's digit be x .

Let the one's digit by y .

Number = ( 10x + y )

A/q ,

x + y = 7 ------( i )

Second case ,

10x + y - 10y - x = 9

=> 9x - 9y = 9

=> 9 ( x - y ) = 9

=> x - y = 1 ---------( ii )

Now eq( i ) + eq ( ii )

x + y + x - y = 7 + 1

= > 2x = 8

= > x = 4

So , y = 7 - x

y = 7 - 4 = 3

so , now required number = 10x + y

= 10(4) + 3

= 40 + 3

= 43 .


:- Thanks :)

Answer 2

Let the ten's digit be x
& one's digit be y

according to the question,

x+y=7..........i

and in second term

10x+y-(10y+x)=9

10x+y-10y-x=9

9x-9y=9

x-y=1........ii

adding i and ii

x+y+x-y=7+1

2x=8

x=4


putting value of x in equation ii

x-y=1

4-y=1

-y=1-4

-y=-3

y=3

the no is 10x+y

10×4+3
=43

43 is the required number.