The length of a rectangular room is 6.5 m in the width is 4.23 meters. what is the perimeter of the room? report the answer with appropriate number of significant digits. -21 meters -21.5 meters -21.46 meters -21.460 meters

The table below shows the approximate masses of a dust particle and a grain of pollen. dust particle 0.000000778 g grain of pollen 0.00000000155 g the mass of a dust particle can be estimated and written in the form a × 10^b, where a = 8 and b = the mass of a grain of pollen can be estimated and written in the form a × 10^b, where a = 2 and b = based on the estimates, the mass of a dust particle is approximately blank times larger than the mass of a grain of pollen.