Rolex buys computer disks at a price of 4 for $5 and sells them at a price of 3 for $5. how many computer disks must he sell to make a profit of $100

Given that Rolex buys computer disks at a price of 4 for $5 .

That means cost price of 1 disk = 5/4

Given that Rolex sells them at a price of 3 for $5.

That means selling price of 1 disk = 5/3

Profit on 1 disk = selling price - cost price

Profit on 1 disk

Profit on 1 disk

Profit on 1 disk

Profit on 1 disk

Now we have to find how many disk to be sold to get the profit $100

so we just divide $100 by profit on 1 disk

Hence final answer is 240 disks.

area of part 1:

a1=base*height/2=(8+2)*(8-2-2-1)/2=10*3/2=15 ft^2

area of part 2:

a2=length*width=(8+2)*1=10 ft2

area of part 3:

a3=length*width=8*2=16 ft2

total shaded area : a1+a2+a3=41 ft2

total area of the reactangle : a=16*8=128 ft2

total area of the nonshaded region : 128-41=87 ft2