Samantha answered 27 questions correctly on her multiple choice math final that had a total of 30 problems. What percentage of questions did Samantha answer correctly on the final exam,

You have to round it down:

4.55 * 1013
4.55 * 1000

and

1.78*1012
1.78*1000

then take them away

so:

4.55*1000= 4550
1.78*1000= 1780 -
                =  2770
                = 2.77*10^3
The antarctic iceberg's mass is approximately 2.77×10³ times bigger than the mass of the rock of Gibraltar.