The number is written in scientific notation.
The significant figures are the numbers known precisely plus 1 digit that is uncertain.
When the numbers are expressed in scientific notation all the digits before 10^n are significant.
So, 7 and 8 are significant figures and the answer is that the number of significant figures is 2.
Answer: 2
The units are nm (nano-meter), km (kilo-meter), pm (pico-meter), dm (decimeter), mm (millimeter), m (meter), cm (centimeter), hm (hectometer) and gm (gigameter). Now we can express each of these units in terms of m.
1 nm = 
, 1 Km = 
1 pm = 
, 1 dm = 0.1 m, 1 mm = 0.001 m, 1 cm = 0.01 m, 1 hm = 100 m, 1 gm = 
. Thus the decreasing unit will be
gm>km>hm>m>dm>cm>mm>nm>pm
It turns out the plane in which the moon moves is related to the plane of earth's orbit around the sun.
