Showing posts from February, 2011

Seniors & juniors algebra word problem

Here's a word problem that someone sent me recently:

The total number of girls in the combined junior and senior classes is equal to the number of boys in those two classes. If the senior class has 400 students and the junior class has 300 students, and if the ratio of boys to girls in the senior class is 5:3, what is the ratio of boys to girls in junior class?
This problem gives a lot of information, and it sounds like it can be solved many different ways. But the first task is to notice what we are given and what we are asked.
We are asked about a ratio. We're given one ratio, and all kinds of totals. There are boys and girls, senior and junior classes. In other words, there are four groups: senior boys, senior girls, junior boys and junior boys.This sounds like it can be solved by setting up some equations and using algebra.

To start, you could for example notice the two facts given about the senior class: The senior class has 400 students and the ratio of boys to girls is 5:…

Chess games into piano music?

I thought some of you might get a kick out of this...
As chess players know, the squares on a chess board are numbered this way:

And this happens to be the same notation as is used in music for notes (A, B, C, D, etc.), the numbers denoting how high the particular note is (in which octave).

So someone came up with the idea of "translating" chess games into music! Here's the link: Chess Music. Provided are three mp3's to listen to as examples of some famous chess games translated into piano music using this method. Kind of funny/interesting. Check also these free online piano lessons (very basic) if you need some.

Lulu birthday - coupon 20% off for MM printed copies

I'll just copy it from Lulu's email to me.. You could use these coupons to purchase Math Mammoth PRINTED versions at a discount.

Enter coupon code HAPPY305 at checkout at LULU and receive 20% off your order. The maximum savings for this offer is $100.

Enter coupon code BIRTHDAY305 at checkout and receive 25% off your order of $500 or more. The maximum savings for this offer is $500.

These great offers expire on February 21, 2011 at 11:59 PM.

Purchase Math Mammoth books at Lulu from this link.

Sorry, but these offers are only valid in US dollars and cannot be applied to previous orders. You can only use these codes once per account, and unfortunately you can't use these coupons in combination with other coupon codes. These great offers expire on February 21, 2011 at 11:59 PM, so don't miss out! While very unlikely, we do reserve the right to change or revoke this offer at anytime, and of course we cannot offer this coupon where it is against the law to do so.

You can see …

World Math Day

World Math Day is coming soon, on March 1, 2011. You need to register beforehand, before February 28.

(Since math is spelled in two different ways (math or maths) around the world,  they even have two different websites, and, but both are the same thing.)

What is World Math Day?

It's a fun worldwide event where students from across the globe compete against each other in answering math facts.

Students play at home and at school against other students around the world in live games of mental arithmetic. Each game lasts for 60 seconds and students can play up to 100 games, earning points for their personal tally. Students can play beyond 100 games during the event, but points will only count to the World Maths Day Mathometer, not their personal point score. The students who answer the most questions correctly appear on the Hall of Fame. There are 5 different levels of play, 20 games on each level.
Schools, students, and homeschoolers can…

A magazine for homeschooled girls

Just passing on a link of a new magazine specifically for homeschooled girls:


My daughter liked the first issue... Go check it out!

They would also like submissions. For example you could send in your daughter's writing assignments or something like that.

Silly graphs (GraphJam)

Just got some good laughs reading the blogpost at SquareCircleZ about funny graphs from GraphJam. Go take a look!

(The GraphJam site itself is not always family-friendly, but the blogpost I'm linking to is fine.)

A percentage problem

Can you help me solve this question?

Jayne is given £5 for her birthday. She spends 30% of it. How much of her birthday money does she spend?
And... Is my method correct for this question? 100-30=70 70/5=14 1.40
No, the asker's method is not correct. In fact, it looks to me like she is randomly doing operations with numbers...

To find 30% of something, one MENTAL MATH method that I like is to first find 10% of that something.

Now, 10% of something is of course 1/10 of it. And to find 1/10 of it, just divide that by 10.

So, we divide £5 by 10 to find 1/10 of £5. It is £0.50. That's 10% of the total. And 30% of the total is three times as much, or £1.50.

So Jayne spent £1.50. See also this video that explains how to find percentages using mental math:

Math Mammoth Light Blue Series bundles for grades 1-3 and 4-6

Now you can purchase Math Mammoth Light Blue series as a bundle for grades 1-3, or for grades 4-6, for a discounted price of $64.

Previously I've had available a bundle for all six grades (and still do), but now you can just grab either the three lower elementary or the three upper elementary grade levels with the same 33% discount.

Please see the order page here.