Question

D. The sum of two digits of a number is 9. If 9 is
subtracted from the number, then the digits are
reversed. The number is:
[AMU: 2001-02]​

Answer 1

Required Answer:-

Given:

• The sum of two digits of a number is 9.
• If 9 is subtracted from the number, the digits are reversed.

To find:

• The number.

Solution:

Let the unit digit of the number be y and the ones digit of the number is x.

Therefore,

➡ x + y = 9 .......(i)

➡ Number = 10x + y

➡ Reversed Number = 10y + x

Now,

➡ Original Number - 9 = Reversed Number.

➡ 10x + y - 10y - x = 9

• ➡ 9(x - y) = 9

➡ x - y = 1 ........(ii)

Adding equations (i) and (ii), we get,

➡ 2x = 10

➡ x = 5

Now,

➡ x + y = 9

➡ 5 + y = 9

➡ y = 4

Therefore, the number is,

= 10 × 5 + 4

= 54

Hence, the number is 54.

Answer:

• The number is 54.

Answer 2

Answer:

And. 4

Step-by-step explanation:

90-9x-9=9x+9

9x+9x=81-9

18x=72

x=72÷18

x=4