數學和Science

Calculator :
Cost = $230 / (1+15%)
= $200

Profit if sold at $250 = [($250 - $200) / $200] * 100%
= 25%

Machine :
Cost = $7,760 / (1 - 3%)
= $8,000

a) Loss if sold at $7,440 = [($7,440 - $8,000) / $8,000] * 100 %
= 7%

b) 10% profit selling price = $8,000 * (1 + 10%)
= $8,800


False
False

Science
True or false
The inner cone of a non-luminous flame contains unburnt town gas. F
A ringing bell stores sound energy. F

Maths
If a calculator was sold at $ 230,then the profit per cent was 15%.What would be the profit per cent if it was sold at $250?

the marked priced (成本):
230/(1+15%)
=$200

the profit per cent:
250-200/200 %
=25%

If a machine is sold at $7760,then the loss per cent is 3%.
a. What is the loss per cent if the machine is sold at $7440?
b. What is the selling price if the machine is sold at a profit of 10%?

a) the marked price:
7760/(1-3%)
=8000

the loss per cent:
[(8000-7440)/8000]*100 %
=4%

b)the selling price:
8000(1+10%)
=$8800