Grace buys notebooks at a price of four for $5 and sells them at a price of three for 6$. How many notebooks must she sell in order to make a profit of $120?

Question

I have no idea how to solve this

Answer 1

Unit cost price=5/4=$1.25 and unit selling price=6/3=$2.

Let x be the number she sells to make a profit of $120.

Profit=sales-cost=2x-1.25x=120.

0.75x=120, x=120/0.75=160.

Let’s check. 160 notebooks @ 4 for $5 cost 40*5=$200.

160 notebooks sell at $2 each making $320, so the profit is 320-200=$120.

Answer 2

For the price bought: $5/4 = $1.25 each

For the price sold: $6/3 = $2 each

For the profit: $2-$1.25=75 cents.

 $120 (12000 cents) / 75c cents (so 12000 divided by 75) is 160.

Answer: 160 notebooks