If a stack of $10 bills is worth $90 billion what is the height of the stack in kilometers? Assume each bill is 0.2 milimeters thick

Question

would the answer be 18,000 km ? 

Answer 1

$90 billion can be written as 9 x 10¹⁰ using scientific notation

 

To determine how many $10 bills there are in the stack, we have to divide 

 

(9 x 10¹⁰) ÷ 10 = 9 x 10⁹

 

Now, we know that 1 km = 1000 m. Also, 1 m = 100 cm. Furthermore, 1 cm = 10 mm.

 

1 km       x    1 m        x     1 cm       so 1 km = 1,000,000 mm = 10⁶ mm

1000 m         100 cm          10 mm

 

Now, to find the height of the stack, we multiply the number of bills times the thickness of each bill:

 

(9 x 10⁹) x (2 x 10^-1) = 18 x 10⁸  = 1800 x 10⁶

 

If 1 km = 10⁶ mm

 

Then 1800 x 10⁶ mm = 1800 km