Question 768206
In {{{ 1.5 }}} min, machine A produces
{{{ 40*1.5 = 60 }}} bolts
-------------
Now, machine B must produce 
{{{ 300 - 60 = 240 }}} bolts
-------------
For machine B,
( number of bolts produced ) = ( rate of producing )*( time spent producing )
Let {{{ t }}} = B's time in mins
{{{ 240 = 30*t }}}
{{{ t = 240/30 }}}
{{{ t = 8 }}} min
------------
The total time to produce 300 bolts is:
{{{ 1.5 + 8 = 9.5 }}} min