Questions

The Chemical name of Gold is Aurum with symbol Au with atomic number 79 and a group 11 element. In its purest form, it is a bright, slightly reddish yellow, dense, soft, malleable, and ductile metal.

Chemically, gold is a transition metal.

Half the Product of Number in the upper & lower box gives the number in the middle box.

i.e. 18 x 4/2 = 36

15 x 6/2 = 45

In the same way 

8 x N/2 = 44 => N = 11.

Gear Lapping is an operation after heat treatment. Gear lapping is the process of imparting a very fine finish and high degree of accuracy to gear teeth, by using a lapping tool and applying a fine-grained abrasive between a work material and a closely fitting surface, called a lapping plate.