# Digit Problems

#### paulmdrdo

##### Active member
The tens digit of a certain two-digit number exceeds the units digit by 4 and is 1 less than twice the units digit. Find the two-digit number.

this is my solution,

let $x=$ tens digit, $x-4=$units digit.

$x=2(x-4)-1$ then, $x=9$ and $9-4=5$

the number is 59

but when I let $x=$ units digit and $x+4=$ tens digit I get the answer of 95.

can you tell me which one is correct?

tnahks!

#### MarkFL

Staff member
Re: digit problems.

I let $T$ be the tens digit and $U$ be the units digit, and so:

$$\displaystyle T=U+4=2U-1\implies U=5\implies T=9$$

And so the two digit number is $95$.

#### Evgeny.Makarov

##### Well-known member
MHB Math Scholar
Re: digit problems.

let $x=$ tens digit... $x=9$ and $9-4=5$

the number is 59
No, it's 95.

#### Deveno

##### Well-known member
MHB Math Scholar
Re: digit problems.

The tens digit of a certain two-digit number exceeds the units digit by 4 and is 1 less than twice the units digit. Find the two-digit number.

this is my solution,

let $x=$ tens digit, $x-4=$units digit.

$x=2(x-4)-1$ then, $x=9$ and $9-4=5$

the number is 59

but when I let $x=$ units digit and $x+4=$ tens digit I get the answer of 95.

can you tell me which one is correct?

tnahks!
In your solution you said: "let $x$ be the tens digit", and then solved for $x$ to obtain $x = 9$.

Thus your number is 9_ (ninety-something).

Solving for the unit digit, which you have as $x - 4$, you obtained: 5.