Assuming that there are nearly 7,000,000,000 (7 billion) people on Earth, estimate the size of number you'd get if you multiplied together the number of fingers on everyone's hands.
For this calculation, it might be easier to count a thumb as a finger. How many zeroes would this number have? How many beaches of sand would this be? How far into the galaxy could we reach if your answer was converted to miles? How many zebras would you need to have this many hairs?
[Ref: ZXZF]
Hint: Think carefully about the people involved, does everyone have 10 fingers?
0, zero, none, nothing.
There is a least one person who has lost all of their fingers on one hand, and so has zero fingers on that hand. So the number we get would be 5 x 5 x 5 x 5 x 5 x 5 x ... x 5 x 0. And anything times zero is zero!

