Question 669994
Let {{{ n }}} = the number of students in the class
given:
2/3 take chemistry, so there are 1/3 remaining
1/3 of those take physics, and that is
{{{ (1/3)*(1/3) = 1/9 }}} of the students
---------------------------------
So far I have {{{ (2/3)*n + (1/9)*n = (7/9)*n }}}
That means there is {{{ n - (7/9)*n = (2/9)*n }}}
students remaining.
-----------------
I am told that {{{ (2/9)*n = 66 }}}
{{{ n = (9/2)*66 }}}
{{{ n = 297 }}}
There are 297 students in the class
------------------------------
check:
2/3 take chemistry
{{{ (2/3)*297 = 198 }}}
There are {{{ 297 - 198 = 99 }}} remaining
1/3 of those take physics
{{{ (1/3)*99 = 33 }}} take physics
There are {{{ 99 - 33 = 66 }}} remaining
and they take biology.
OK