Redemption for Opener 8/29/16

 A ton of TNT will release 4.2 × 10⁹ J (joules). Express this energy in megajoules.

• 4.2 x 10¹⁵ MJ
• 4.2 x 10³ MJ
• 4.2 x 10^-15 MJ
• 4.2 x 10^-3 MJ

 In SI units, a parsec equals 3.086 × 10¹⁶ m. Express this distance in kilometers.

• 3.086 x 10¹⁹ km
• 3.086 x 10¹³ km

The entire floor area of the Pentagon equals 0.344 279 km² . Express this area in square millimeters.

• 3.442 79 x 10^-6 mm²
• 3.442 79 x 10⁵ mm²
• 3.442 79 x 10¹¹ mm²
• 3.442 79 x 10^-13 mm²

Identify the number with 3 significant figures.

• .003
• 20300
• 800
• 310

Round the following number to 4 significant figures:  324 654.743

• 324 600.000
• 324 600
• 4.743