Question

The tens digit is y and the units digit is one half of that. What is the value of the number if I reverse its digits ?

Answer 1

The number after reversing the digits is
`\bold{6y}`

Explanation:

First of all, let us try to learn about representing a 2 digit number.

28 can be written as 20 + 8 OR 2
`*` 10 + 8

79 can be written as 70 + 9 OR 7
`*` 10 + 9

17 can be written as 10 + 7 OR 1
`*` 10 + 7

i.e. if we are given the unit's and ten's digits as U and T, we can write the two digit number as: T
`*` 10 + U

Now, it is given that ten's digit is
`y`.

Unit's digit is half of that i.e.
`(y)/(2)`.

So, the number is

`y * 10 +(y)/(2)\\\Rightarrow 10 y +(y)/(2)\\\Rightarrow (21)/(2)y`

Now, the digits are reversed:

Unit's digit =
`y`

Ten's digit =
`(y)/(2)`

So, the number after reversing the digits:

`(y)/(2)* 10+y\\\Rightarrow 5y+y = \bold{6y}`

The number after reversing the digits is
`\bold{6y}`.