 What you need to know

Things to remember:

• It is helpful to think of the time as years first and then convert to other time units.

Before we start, it is important to know how long certain periods of time are.

Time Unit                    Number of Years

1 century                     100

1 millennium                1000

When converting time units into years, we can think of this just like we have when converting measurements.

Time Unit                     Multiply by                   Number of Years

1 century                          100                                         100

1 millennium                    1000                                       1000

What is 7 decades in years?

$$7\times10=70$$

7 decades is the same as 7 years.

What is 2.27 centuries in years?

$$2.27\times100=227$$

2.27 centuries is the same as 227 years.

What is 3.2 millennia in years?

$$3.2\times1000=3200$$

3.2 millennia is the same as 3200 years.

But, like with converting units, we can also go the other way by dividing.

Years to Decades                               Divide by 10

Years to Centuries                             Divide by 100

Years to Millenia                               Divide by 1000

How many decades are there in 75 years?

$$75\div10=7.5$$

There are 7.5 decades in 75 years.

How many centuries are there in 600 years?

$$600\div100=6$$

There are 6 centuries in 600 years.

How many millennia are there in 350 years?

$$350\div1000=0.35$$

There are 0.35 decades in 350 years.

Example Questions

$$6.33\times100=633$$

6.33 centuries is the same as 633 years.

$$4200\div1000=4.2$$

There are 4.2 millennia in 4200 years.