Rib stitch over an odd number of stitches is worked the same as for rib stitch over an even number of stitches—by alternating knits and purls. The difference is that when you cast on an odd number of stitches, you will end the row with the same stitch you began it with. This means if you start the row with a knit stitch you will end it with a knit stitch.
Step by step
Don’t forget that you will work stitches as they appear. This mean, when there’s a knit stitch, you will knit it, and when there’s a purl stitch, you will purl it. If you were to work the stitches in the opposite stitch as they appear, you would be knitting in seed stitch.
Start by working a knit stitch…
… bring the yarn to the front and purl a stitch…
… place the yarn in the back and knit a stitch.
Continue alternating knit and purl stitches until you reach the end of the row.
Turn your work, and since you have an odd number of stitches, all the wrong side rows will begin and end with a purl stitch.
... place the yarn behind your work and knit one…
… bring the yarn to the front and purl one…Continue alternating knit and purl stitches, working the stitches as they appear.