My daughter is doing a research project for her 7th grade class.  We
need to know if we can grow a new carrot from cutting off the top of
an existing carrot and the technique in doing so.

Greetings, cheyenne!

You certainly can grow carrots from a discarded carrot-top; this has
been a favorite grade-school project for decades (I did it myself with
carrots and avocados when I was young!). I found that this works best
if you use a carrot with the greens still attached at the top.

I found a site for you with a good description on how to do this.

From the Jewish Nature Center's section on "Indoor Gardens":
"You can use the same technique to grow carrots or horseradish. Just
cut the top [leaving ½-to 1-inch of carrot under the leaves] and place
in a saucer of water, place this in a clear plastic bag and cover. If
water levels should drop, open and replenish. It will not be long
before you begin to see new growth.  Transplant when leaves start to
grow or when the roots fill the cup."
http://www.jewishnaturecenter.org/html/indoor_gardens.html


Search Strategy

"grow carrots" from top
://www.google.com/search?q=%22grow+carrots%22+from+top


I hope that this Answer provides you with exactly the information that
you were seeking, and wish you great luck (and a green thumb) for your
fledgling carrot crop!

Regards,

aceresearcher

Thank you very much aceresearcher for your prompt and concise answer
along with the link to the website. This will definately help us. 
Thankyou again.

Cheyenne,

Thank YOU for the excellent rating and the tip. I am delighted that
you found my answer helpful!

ace