Showing posts from July, 2012

Math Mammoth in Cathy Duffy's 101 Top Picks!

You might have heard of this popular homeschool book, 100 Top Picks for Homeschool Curriculum by Cathy Duffy. Math Mammoth has been included as one of the top picks for the newest edition of this book, just coming out!

I feel honored about it... years ago, when I started working with the books, I never DREAMED it would come to this!

If you're interested in the new edition of book, Homeschool Buyers Co-op has a group buy for its digital version, ending at the end of this month.

And, if you subscribe to Cathy's newsletter at, you get a $3 discount coupon code for the printed version, I understood.

You can read her review of Math Mammoth in the book, of course, but also on her website as well:

The Fibonacci numbers and converting miles to kilometers

This is an INTERESTING application of Fibonacci numbers!

Fibonacci numbers are the sequence
1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, and so on. (Add two numbers in the sequence to get the next one.)

Take two neighboring numbers in the sequence, such as 5 and 8. Turns out, 5 miles is approximately 8 km.  Take 34 and 55:  34 miles is about 55 km.

If your number is not in the sequence, write it as a sum of numbers that are:

Convert 10 miles into kilometers. 10 = 5 + 5, and 5 miles is about 8 km. So, 10 miles is about 16 km.


Convert 25 kilometers into miles. 25 = 21 + 2 + 2.

21 km = 13 miles (about)
2 km = 1 mile (about)
2 km = 1 mile (about)

25 km = about 13 + 1 + 1 miles = about 15 miles.

More details here: Adventures in Fibonacci Numbers

The reason has to do with the fact that the conversion factor, (0.621371192 mi/km) is pretty close to the ratio to which sequential Fibonacci numbers converge (0.61803).

Math Mammoth Grade 3 now aligned to the Common Core standards

Math Mammoth Grade 3 is now aligned to the Common Core. In this post I try to outline what is same and what is different about this edition compared to the previous one.

What is same?

-  The focus on single-digit multiplication and division is the same. I did add more varied word problems to these two sections, and other little 'enhancements' as I edited the lessons, but no major changes here.

- Also, much of the addition,  subtraction, and place value topics are the same. There are some slight differences, yes, but not major ones.

- Time and money sections are the same.

What is different?

- The geometry chapter has been pretty much redone. Now, it concentrates on the concepts of area and perimeter (according to Common Core standards). Before, I did have one lesson on area, but also other concepts, such as right angles and parallel lines. Those will be moved to 4th grade.

- In measuring, I have removed most of the content that dealt with conversions between the measuring units, …