Posts

Showing posts from September, 2010

Math Mammoth Geometry 2 giveaway

Image
Recently I offered one of my customers a free book for finding an error in the answer key... she declined and wished someone else could have it who is in need.

So I'll give one electronic copy of Math Mammoth Geometry 2 book (PDF file) to one randomly chosen lucky winner.

To participate, you need to do two things:
1) Leave a comment in this blogpost, explaining how and where you'd use this book, AND
2) Email me so I have your email address.

If you have no use for this geometry material, please don't participate, and let someone win who can use it.

If I choose a winner who didn't email me, then I cannot contact them. In that case I will have to choose another winner.

I'll first choose a few best entries based on how/where they'd use the book, and then choose randomly among those.

This 'contest' closes and winner will be chosen whenever I notice (in checking my mail) that there are at least 10 participants. So hurry up!

Free math tutoring

David Freeling from TutorTalk.org wants to let us know that as a part of a promotion to launch his site, he's offering FREE tutoring on every Friday.

Here is some information from David:

Free tutoring will apply to specific classes, labeled as Free. Students should visit www.TutorTalk.org in advance and register, because space is limited. Free lessons cover fundamental math, reading and writing skills and are suitable for a wide range of ages, but especially middle and high school. Curriculum focuses on problem-solving, and kids are encouraged to play along from home and be prepared with a calculator, pen and paper. Students will also be able to bring in their own homework problems for small group tutoring, in classes of up to 5 students.

The site also says, "TutorTalk Classes are dynamic, interactive small-group classrooms, led by a qualified teacher, and hosting up to five students. Students work together and chat to solve onscreen problems from the comfort of their own h…

Homeschooling by the Numbers

Image
My dh found an interesting "infographic" about homeschooling statistics. Click the image to enlarge.

Integer games online

I have updated the list of integer games online at my site. Now the games are organized into sections of:
ordering integers, addition & subtraction of integers, multiplication & division of integers, and all operations with integers. Happy playtime!

How to use an abacus with Math Mammoth

Image
I've received several questions about abacus usage in Math Mammoth curriculum. Here are some thoughts about it:

The only way the abacus is used in my books is so that each bead counts as one. Nothing fancy. It is NOT used like Chinese or Russian abaci where one bead might count as 5, 10, or 100.

A 100-bead abacus or school abacus simply contains 10 beads on 10 rods, a total of 100. Each bead simply represents one. The 100-bead abacus lets children both see and touch the numbers.

First and foremost, the abacus is used in the place value chapter in 1st grade where children learn about tens and ones (numbers up to 100). We use it to show how 45 is made up of 4 tens and 5 ones, for example.

Secondly, you can use the abacus with addition and subtraction problems in 1st and 2nd grade:
Show the child additions and subtractions with whole tens. For example, to solve 50 + 20, first make 50 on the abacus. Then add 20 more.Add a two-digit number and a single-digit number. For example…

Order of operations / PEMDAS

Image
Someone asked me recently...

Could you please share with me your opinion of the "Please Excuse My Dear Aunt Sally" simplifying expressions. Any feedback could you give will be appreciated. Thank you.

This "PEMDAS" rule is a mnemonic for order of operations:

Please = Parenthesis
Excuse = Exponents
My = Multiplication
Dear = Division
Aunt = Addition
Sally = Subtraction

There's nothing wrong with using a mnemonic to remember the order of operations. However, one has to bear in mind that

This rule is not all-inclusive. It omits for example square roots. But the rule is good for all elementary grades. (Square roots would be on the same level or rank with exponents, by the way.)
The rule doesn't spell out the fact that in reality multiplication and division are "on the same level" or rank. This means that if you have several multiplications and divisions, you do them from left to right, and not "multiplication first, then division".

For example…

Estimation methods

Image
A typical estimation problem:
guess how many paper clips are in a jar?
Photo by Dean Terry
Here recently I was asked a question about estimation methods:
My daughter's homework was to estimate the number of 953 divided by 18, using front-end estimation, using rounding to estimate, and using compatible numbers to estimate. What are the differences between these three methods? Do we get the same result? Thanks!

You definitely don't get the same results as these three methods are quite different!

Front-end estimation means you keep the "front" or first digit of each number, and make the other digits to be zeros.

So, 953 ÷ 18 is estimated to 900 ÷ 10 = 90.

Another example: 56 × 295 would be estimated as 50 × 200 = 10,000.

Rounding means you round the numbers, usually to their biggest place values, but sometimes you can round "creatively". In any case, the numbers you round to should be easy to work with mentally.

So, in 953 divided by 18 we round 953 to nearest…