64) If the lead screw has 6 T.P.I. and if there are 4 numbered divisions in the chasing dial, the number of teeth in the worm wheel of the casting dial will be

65) For selecting the gears required to cut a 3 mm pitch thread on a job in a lathe having a lead screw of 6 mm pitch and a driver gear of 60 deeth, the driven gear shall have _____ number of teeth.

66) The mass of a cylindrical job of steel with a diameter of 20 mm and length 50 mm is about _____ g. Density of steel is 8 g/cc.

67) The angle inscribed in a semicircle is always _____ degrees.

68) How many square of size 100 mm x 100 mm can be cut from a sheet of size 500 mm x 1000 mm?