Mathematics F1 (Come in)

1.The marked price of a mobile phone is increased by its cost by 25%. If it is
sold at 20% off, the selling price is $2500. Find .

The cost price:

2500 / ( 1 - 20% ) / ( 1 + 25% )

=2500 x 1.25 x 0.8

=$2500

Let $y be the cost price.
y(1+25%)(1-0.8%) = 2500
(1.25×0.8)y = 2500
y = 2500/(1.25×0.8)
y = 2500
∴The cost price is $2500.

Let Y be amount
Y(1+25%)(1-20%)=250
(1.25)(0.8)Y=2500
1Y=2500
Y=2500

the cost price is $2500

$2,500X1.2/1.25
=$3,000/1.25
=$2,400