<PRE><B>Question 888167</B>
Girls / boys = 2/3 
This means 2 out of every 5 students is a girl, and
3 out of every 5 students is a boy
{{{ (3/5)*40 = 24 }}} students are boys
--------------------------------------
Now there are {{{ 40 + 5 = 45 }}} students
girls / boys = 4/5
5 out of every 9 students are boys
{{{ (5/9)*45 = 25 }}} students are now boys ( answer )
That means that 1 of the 5 new students was a boy
-----------------------------------------------
check:
4 of the 5 new students was a girl
There were {{{ 40 - 24 = 16 girls }}}
{{{ 16 + 4 = 20 }}}
-------------------
The new ratio is 4/5
{{{ 20 / 25 = 4/5 }}}
{{{ 4/5 = 4/5 }}}
OK
</PRE>