That may be enough if you use the larger needle, or even a size 9 or 10, but for a regular 6" scarf. Only you can know how much you use. You could CO 20 sts, knit for 4 inches, measure the width and length to see how many square inches that is. Then measure how much yarn that took and divide 720 sq inches by the sq inches you got and multiply that by the yarns it to you to make your sample. 10" is pretty wide though, most scarves are generally 6-8" wide. So casting on the 20 sts should let you see how wide that turns out and figure out if you actually do want it 10" wide.
sue- knitting heretic