Select the number that matches the written value: three hundred twenty-one thousandths

0.321

To find the number that matches the written value "three hundred twenty-one thousandths," we need to understand place value. Let's break down the written value:

- "Three hundred" means we have 300.
- "Twenty" means we have 20.
- "One thousandths" means we have a fraction out of 1,000.

Combining these parts, we have 300 + 20 + a fraction out of 1,000.

To convert the fraction "one thousandths" to a decimal, we need to divide the numerator (1) by the denominator (1,000):

1 รท 1,000 = 0.001

Now we can add all the parts together:

300 + 20 + 0.001 = 320.001

Therefore, the number that matches the written value "three hundred twenty-one thousandths" is 320.001.