Answer
a- 127 Å = 1.27 x $10^{-10}$ cm
b - 21.0 kg = 2.1 x $10^{7}$ mg
c- 1.09 x $10^{1}$ mm
d- 4.6ns = 4.6 x $10^{-3}$ ms
Work Step by Step
a - 127 Angstrom to centimeter
127 Å = 127 x $\frac{10^{-10}(m) }{1Å}$ x $\frac{10^{-2}(cm)}{1m}$ = 127 x $10^{-12}$ cm
or 127 Å = 1.27 x $10^{-10}$ cm
b - 21.0 kg to milligrams
21.0 kg = 21.0 kg x $\frac{10^{3}g}{1kg}$x $\frac{10^{3}mg}{1g}$ = 21 x $10^{6}$ mg
or 21.0 kg = 2.1 x $10^{7}$ mg
c - 1.09 cm to millimeters
1.09 cm = 1.09 cm x $\frac{1m}{10^{2}cm}$ x $\frac{10^{3}mm}{1m}$ = 1.09 x $10^{1}$ mm
d - 4.6ns to microseconds
4.6 ns = 4.6 ns x $\frac{1s}{10^{9}ns}$ x $\frac{10^{6}µs}{1s}$
4.6ns = 4.6 x $10^{-3}$ ms
