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Summer Game #3: Piggyback Race

How’s your summer been? I was at a family reunion in Prescott, Wisconsin last weekend. We had four generations that day at the farm that my grandparents purchased many many years ago. My dad grew up on this patch of heaven, his sister and husband ... Read More

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Dr. Cotter on Subtraction Approaches

There are at least eight different ways to subtract multi-digit numbers. Even though a person has learned one method, it is good to explore other methods to enhance understanding. If a child has an accurate and efficient method of subtraction, do ... Read More

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Summer Game #2: Math Balance Addition

So how’s the summer so far? It’s been great up here in Hazelton, North Dakota. The days are getting long – almost 16 hours of official sunlight! First light is at 5:10 am and last light is 10:09 pm, so it’s even longer when you’re outside and ... Read More

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Summer Game #1: Make 16 Cents

It’s summer time again!! School is out (or almost out), the grass is green, flowers are blooming, and the water is ready for the fun to begin! Like last year, we’re going to have a Summer Game series. These weekly games will help the kids keep ... Read More


Dr. Cotter on What 6 × 3 Means

Sometimes 6 × 3 is thought of as “6 groups of 3.” However, consistency with the other arithmetic operations requires a second look. When adding 6 + 3, we start with 6 and transform it by adding 3. When subtracting 6 – 3, we start with 6 and transform ... Read More

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Level G, Lesson 154

Susan wrote us: “Hello, my son and I are struggling with Lesson 154, with problems 9 & 10. Can we please have an explanation? Love your materials! Thank you.” Well, Susan, this took me a while to come up with a good clear explanation! Here’s ... Read More