home work help......?

Question

please help me in finding out the ans of this maths problem.I am in class 8 so please explain also ..
''a shopkeeper offers 10% off season discount to the customers and still makes a profit of 28%.what is the costprice of the pair of shoes marked at 1120$."

Answer 1

cost * 1.28 = .9 (sell)
cost * 1.28 = .9 (1120)
cost = .9 * 1120 / 1.28
cost = $787.50

Answer 2

I think you have a typo, the shoes were probably marked at $110.
But if the price really is $1120, the idea is the same.

So a 10% discount would be 10% off the $1120. So the actual price to the customer would be 90% of the $1120.
So that would be .9 x 1120 or $1008.

If he makes a profit of 28%, that means the cost to him is the difference between 100% and 28% (its called the reciprocal) or 72%. His cost then is 72% of the ticket price to the customer ($1008) or $725.76.

Answer 3

a 10% discount off $1120
is
1120 * ((100-10)/100)
=1120 * (90/100)
=1120 * 0.9
=1008

he sells at $1008

he makes 28% profit so

the sale price minus the profit is the cost
and the profit is 28% of the cost

cost = sale price - (28% of cost)
let cost = c

c= 1008 -0.28c
c + 0.28c = 1008 (add 0.28c to both sides)
1.28c=1008 (1c+0.28c=1.28c)
1.28c/1.28=1008/1.28 (divide both sides by 1.28)
c=1008/1.28
c=787.5

cost is $787.50

remember that what you do to one side of an equation you have to do to the other side.