Is there much of a difference between 99.9% or 99.999%?

Use our present need for cleanliness to engage your students.

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Does it really matter whether you kill 99.9% of the bacteria or 99.999% of the germs?

In this 3-act activity we've asked students to consider whether these claims about these two wipes' efficacy really make a difference.  We've supplied students with a list of bacteria counts on various surfaces and asked them to calculate how much of a difference these two different percents make in wiping out germs.

This is an excellent opportunity to deal with repeating decimals.  

The Activity: KillingGerms-2020.pdf

CCSS: 5.NBT.3, 5.NBT.7, 6.NS.3, 7.NS.2.d, 8.NS.1

For members we have an editable Word docx, an Excel sheet with data and calculations, and solutions.

KillingGerms-2020.docx    bacteria-count2020.xlsx    KillingGerms-solution2020.pdf


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