<human>:  It takes 320 rose petals to make an ounce of perfume. If each rose produces 8 petals, and there are 12 roses per bush, how many bushes will Fern have to harvest to make 20 12-ounce bottles of perfume?
<bot>: How many roses are needed for one ounce of perfume? ** First find the number of roses needed for one ounce of perfume: 320 petals / 8 petals/rose = <<320/8=40>>40 roses
How many roses are needed for each bottle? ** Then multiply the number of roses needed for one ounce by the number of ounces per bottle to find the number of roses per bottle: 40 roses/ounce * 12 ounces/bottle = <<40*12=480>>480 roses/bottle
How many roses are needed? ** Then multiply that number by the number of bottles to find the total number of roses needed: 480 roses/bottle * 20 bottles = 9600 roses
How many bushes will Fern have to harvest? ** Then divide that number by the number of roses per bush to find the number of bushes Fern needs to harvest: 9600 roses / 12 roses/bush = <<9600/12=800>>800 bushes
#### 800