Question

If seven times a two digit number is four times the number obtained by reversing its digits . if the difference of the digits is 3 , find the numbers?

Answer 1

let the number be xy

7xy = 4yx

7(10x + y) = 4(10y + x)

70x + 7y = 40y + 4x

66x = 33y

2x = y

now: x-y = 3
        x - 2x = 3
        -x = 3
x = -3

therefore, 
-3-y = 3
-y = 6
y=-6.

therefore the number is 36

Answer 2

Answer:

36

Step-by-step explanation:

Let the unit digit be a and tenth unit be b .

So , number = 10 b + a

It's said number is seven times is equal to reversing the order of its digit.

= > 7 ( 10 b + a ) = 4 ( 10 a + b )

= > 70 b + 7 a = 40 a + 4 b

= > 66 b = 33 a

= > a = 2 b ... ( i )

Also given numbers' difference is 3 .

a - b = 3  ( ii )

From ( i ) and ( ii ) we get :

a b - b = 3

b = 3

= > a = 6

Hence number = > 30 + 6

= > 36.