Rates of descent are easily worked out on the whizz wheel (that wonderful device used by professionals; i.e. navigators). If the glide slope angle is given in degrees put the 60 on the inner scale next to glide slope angle on the outer scale. If it is given as a percentage put the 10 on the inner scale next to the glide slope percentage on the outer scale. Now go to the groundspeed in knots on the inner scale and next to it is rate of descent in feet per minute on the outer scale.