Reply To: 1-5 – Relating Fractions, Decimals, and Percents – Discussion

[Katrien Vance]

I have two very bright math students working with me this summer to finish Algebra 1. They see patterns quickly and apply new ideas beautifully. We came to a screeching halt when we were working on Greatest Possible Error, and I gave a measurement of 7.5 cm. They knew that the GPE should be one-half of one-tenth of a centimeter, but then their faces were like . . . does not compute . . . One girl said, “One twentieth of a centimeter?” But then how to write that as a decimal? When I wrote 0.10 instead of 0.1 (as my unit of measure), that opened the door–1/10 = 10/100. And half of ten one-hundredths is . . . well, then it was easy. It was so interesting to see how it’s not the grand concepts that are challenging but these basic fundamentals–how do you write 1/2 of 1/10 as a decimal? Oof. It’s right back to place value and also to the language we choose to use. Having the flexibility to see 10/100 as the same thing as 1/10 was the key.