Question 896327
The difference between a 2- digit number and the number obtained by interchanging its digits is 27. 
<pre>
{{{(10t+u)-(10u+t) = 27}}}
{{{10t+u-10u-t = 27}}}
{{{9t-9u = 27}}}
{{{t-u = 3}}}

This tells us that t is larger than u, which we'll need
to know for the next part:

...the ratio between the digits of the number is 1:2 ?

Since t is larger than u we know that this means

{{{u/t=1/2}}} and not {{{cross(t/u=1/2)}}}


{{{u/t=1/2}}}
{{{2u=t}}}

So we have the system of two equations:

{{{system(t-u=3,2u=t)}}}

Solve by substituting:

{{{t-u=3}}}
{{{2u-u=3}}}
{{{u=3}}}

{{{2u=t}}}
{{{2(3)=t}}}
{{{6=t}}}

So the number is 63.

Edwin</pre>