form1 math question

A man sells two machines at $19 800 each. He makes a profit of 10% on one machine and suffers a loss of 10% on the other. On the whole, find
(a) his profit or loss,
(b) his profit % or loss %
(a)
the total cost
=19800/1.1+19800/0.9
=18000+22000
=40000
the total amount he receive
=19800*2
=39600
he loss
(b)
his loss %
=(39600-40000)/40000
=-0.1
=-10%


2006-12-08 21:24:28 補充：
his loss %=(39600-40000)/40000=-0.01=-1%

a) His profit
= profit of first machine + profit of second machine
= [19800 - 19800/110% ] + [19800 - 19800/ 90% ]
= 1800 - 2200
= -400

so, his LOSS = $400

b)
cost of the two machine = 19800 * 2 +400 =40000

loss percentage
400
=---------- x 100%
40000

= 1%