MathBench > Microbiology

Viable Plate Count, or...
How to count to a million

Overall dilution

Now that you are very comfortable with dilution factors... what happens if you dilute and then dilute again? For example, we could take super-strong cofee, dilute it by 1/5, then dilute THAT by 1/10. So,

can you do it in your sleep?Here's the rule:

To find the overall (or total) dilution factor,
simply multiply the dilution factors for each step.

Once again, here's an applet to practice finding the total dilution scheme, regardless of how the dilution scheme is expressed -- as directions, as fractions, or as decimals.

Remember, keep going until you're very comfortable with the calculations... Oh, and do yourself a favor, use a calculator!!

Given the following series of dilutions,
what is the total dilution factor?

As a Fraction: 1 /
As a Decimal:
feedback here