Question number 9, page 51, volume 4 curiculum 840, its, understand, product, number

Darien

Can any explain for me why to get par value of the 10-year bond, we take dellar duration of the 5-year ($454,840) divide by the product of the duration of the 10-year and its quoted price and 0.01 to get the par value of the 10-year.
I don’t not really understand the logic behid doing this.
Thanks,