Counting the shaded squares, we see that 78 out of 100 is shaded.
Now,
That is
78/100
In decimal,
78/100=0.78
first answer is correct.
0.7800 --- this is correct as well because we can drop the last zeros, they aren't significant.
0.078
If you get its fraction, you will see that it is:
78/1000, which is not what we want.
Thus, this option isn't correct!
