What is the common ratio of the sequence 3, 21, 147, … ?

The common ratio is a constant found in geometric sequences, denoted r in the equations for geometric sequences, when any term is divided by the term preceding it.  In this case the common ratio is:

147/21=21/3=7=r

So 7 is the common ratio.

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.

The answer is