Question

Sum of the digit of a two digit number is 7.If 9 is added to the number.Its digits are reversed.Find the number

Answer 1

Answer:

n+m=7 ———————→eqn 1

10n+m+27=10m+n

m=7-n

10n+(7n)+27=10(7-n)

9n+34=70–9n

18n=36

n=36÷18

n=2

Now sub n=2 in eqn 1

2+m=7

m=7–2

m=5

n=2 ; m=5.

Step-by-step explanation:

Answer 2

34

Step-by-step explanation:

Let first digit be x and second digit be y .

Let original no be = 10 x X + Y

A/Q

1.   X + Y = 7

X= 7-Y

2.  10 x X + Y + 9 = 10 x Y + X

10X + Y + 9 = 10Y + X

10X - X + 9 = 10Y - Y

9X + 9 = 9Y

9X - 9Y = -9

X - Y = -1

7-Y-Y = -1

-2Y = -1- -7

-2Y = -8

Y = 4

X = 7-4

 = 3

Original no = 34