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Digit Problems

paulmdrdo

Active member
May 13, 2013
386
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

Administrator
Staff member
Feb 24, 2012
13,775
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
Jan 30, 2012
2,502

Deveno

Well-known member
MHB Math Scholar
Feb 15, 2012
1,967
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.

Thus your number is 95.

You solved it correctly, but misinterpreted your own solution.