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Showing posts from April, 2011

A woman without hands - inspiring!

An inspiring slideshow about Jessica Cox - a woman born without hands. She even learned to fly!

Jessica cox english.pps

A new template

Hope you like it! I just chose one that Blogger offers. They sure have improved their templates in the last few years because when I signed up with Blogger years ago, the templates were kind of lame... much better now.

How to help a student with a fraction word problem

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Today, my daughter had to tackle this word problem in her 5th grade Math Mammoth (lesson Multiply Mixed Numbers):

The square on the right measures 10 in. × 10 in. and
the rectangle inside it measures 6 7/8 in. × 3 1/2 in.
How many square inches is the colored area?
This requires the student to
multiply mixed numbers, subtract mixed numbers, understand about area, and understand how to find the "colored" area by subtraction of areas. 
So it is a multi-step word problem.

She didn't understand it, she said. My first "help" was this:
"Let's say we change those fractions to whole numbers 6 and 3. Can you mark those in the image? Would you be able to solve the problem now?"

The strategy I used is:
If you can't solve the problem at hand, change it and make it easier. Then try to solve the easier problem.

She was able to mark 6 and 3 on the sides of the rectangle (that is inside the square). But she said she couldn't solve it. She said it's not p…

Decimals videos

Here are some of my recent additions to Math Mammoth Youtube channel.
 - videos about decimal arithmetic.

Add and subtract decimals
I explain the main principle in adding or subtracting decimals: we can add or subtract "as if" there was no decimal point IF the decimals have the same kind of parts--either tenths, hundredths, or thousandths. Many students have a misconception of thinking of the "part" after the decimal point as "plain numbers." Such students will calculate 0.7 + 0.05 = 0.12, which is wrong, and I explain why in the video.






Multiply decimals by whole numbers
I explain how to multiply decimals by whole numbers: think of your decimal as so many "tenths", "hundredths", or "thousandths", and simply multiply as if there was no decimal point. Compare to multiplying so many "apples". For example, 5 x 0.06 is five copies of six "hundredths". Multiply 5 x 6 = 30. The answer has to be 30 hundredths (hund…

Green tea word problem

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Photo credit: leojmelsrub
Ahmed sent me in this kind of word problem:


A tea producer want to market mixed green tea leaves at $14 per pound. how many pounds of high mountain green tea leaves worth $20 per pound must be mixed with 90 pounds of regular green tea leaved worth $10 per pound?

I have solve many problems like this one on my blog, but it never hurts to solve some more. This can be solved with algebra, using a chart. I've done that before for similar problems... so if you are reading this, and you feel a bit "rusty" in this area, try to make the chart yourself first, before you read further!

For the chart, we also need to choose a variable or several. In this case it is easy:  the unknown is obviously what is asked, or the amount of high mountain green tea. Note also that the cost is always the price per pound times the amount.


mountain green regular green the mixture tea leaves tea leaves -----------------------------------------------------------------------…

Math vocabulary resource

Would you like to help children with their math vocabulary? SpellingCity has built a resource to address this: Math vocabulary spelling lists.

If you don't know SpellingCity, no matter what kind of spelling list you use, you can always practice the words in many ways: either just simple practice AND with several different games: MatchIt Sentences, Which Word (find which word correctly completes the sentence), sentence unscramble, hang mouse, word search, word unscramble, etc. Can't even list them all.
So it is definitely a very comprehensive math vocabulary resource!

Two problems about fractional parts

I have 2 questions on fractions which I can't solve.

There were 3/5 as many adults as children on a bus. At the next bus stop, 6 adults and 6 children boarded the bus. As a result, there were 2/3 as many adults as children on the bus. How many people were on the bus at first?
A solution using bar diagrams (Singapore style):

children |----|----|----|----|----| adults |----|----|----| Then we have:

children |----|----|----|----|----| +6 adults |----|----|----| +6
Here look at the difference of children and adults. There are two "blocks" more children than adults. We know the number of adults is 2/3 of the number of children... therefore the DIFFERENCE of two blocks must be 1/3 of the children.

Now look:
children |----|----|----|----|----| +6Two of those blocks is 1/3 of the total... the other two blocks is another 1/3 of the total... so |----| +6 or one block and 6 must be 1/3 of the total.
This means the +6 must be one block. Or, one block = 6. This now solves the proble…