Mg(OH)2 is the correct chemical formula because it takes two Hydroxide ions to bond with Magnesium normally it would be written with a subscript number 2 rather than the parenthesis and number 2
1 meter = .001 kilometers so 4.5 x 10^3 = 4500 so .001 x 4500 = 4.5 kilo
C. Cello playing music at a concert
