Question 964047
Set a = average weight of the 60 students
So 60*a is the weight of the entire class
(60a - 45kg ) = The weight of the remaining 59 students
(60a - 45kg)/59 = a + 200g
or converting to kg
(60a - 45kg)/59 = a + 0.200kg
The left hand side is the average weight of the remaining 59.
This average is 200g more than the previous average.
Now let us solve.
{{{(60a - 45)/59 = a + 0.200}}}
{{{(60a - 45)/59 = (a + 0.200)/1}}}
{{{59(a+0.2)=(60a-45)}}}
{{{59a+11.8=60a-45}}}
add -59a to each side
{{{11.8=a-45}}}
add 45 to each side
{{{11.8=a-45}}}
{{{56.8=a}}}
Since the average weight of the 59 is a + 0.200kg,
the average weight is 56.8 + 0.2 = 57kg