Question

The Mississippi River is about 4,000 kilometers long. An M&M is about 1 centimeter long. There are 100 centimeters in a meter, and 1,000 meters in a kilometer. Estimate how many M&Ms it would take to measure the length of the Mississippi River

Answer 1

To be able to determine the number of M&Ms that are needed in order to measure the length of Mississippi River, we convert the units to a common one. For this purpose, we convert kilometers to centimeter such that,
 
Length of Mississippi River = (4000 km)(1000 m/1 km)(100 cm/1 m)
                       = 400,000,000 cm

Since there are 400,000,000 cm in the entire length of the river, the answer would also be 400,000,000.