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

Answer:

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

Step-by-step explanation:

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

28 can be written as 20 + 8 OR 2 $\times$ 10 + 8

79 can be written as 70 + 9 OR 7 $\times$ 10 + 9

17 can be written as 10 + 7 OR 1 $\times$ 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 $\times$ 10 + U

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

Unit's digit is half of that i.e. $\frac{y}{2}$.

So, the number is

$y \times 10 +\frac{y}{2}\\\Rightarrow 10 y +\frac{y}{2}\\\Rightarrow \dfrac{21}{2}y$

Now, the digits are reversed:

Unit's digit = $y$

Ten's digit = $\frac{y}{2}$

So, the number after reversing the digits:

$\dfrac{y}{2}\times 10+y\\\Rightarrow 5y+y = \bold{6y}$

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