Quick Calculations - Use Half and Double

 

 

                                           X        


Work smart, not hard!

Double the...

... to...

 and halve the ...
 
 
 

... to...

 

 

100 X 8 = 800. Done!

 

Double/Double or Double/Double/Double

Are you multiplying by 4 or 8? 


Dividing by 4 or 8?


If you are multiplying by 4, think double/double.

So... 6 X 4? 

(No expense spared here at the RUGS Blog for our state of the art graphics.)

Double 6 = 12 and double 12 = 24. 

So 6 x 4 = 24.

4 x 8?

If you are multiplying by 8, think double/double/double.

Double 4 = 8 and double 8 = 16 and double 16 = 32. 

So 4 x 8 = 32.

If you are dividing by 4, think half/half.

So... 24 divided by 4? 

half of 24 is 12 and half of 12 is 6 

24 divided by 4 is 6

If you are dividing by 8, think half/half/half.

So... 24 divided by 8? 

half of 24 is 12 and half of 12 is 6 and half of 6 is 3

24 divided by 8 is 3

D.L.M.R. - Work Smart, Not Hard!

Work Smart, Not Hard!

Remember DLMR. Here's some suggestions for DLMR...

Does Love Mean Rules?

Do Like Mother Recommends

Doughnuts Leave Me Retching

Do Like My Rap!

Ducks Like Marshy Rivers

Dogs Like My Rug

Doug Lost My Respect

Digital Listening Mobile Radio

Don't Like My Ride

Down Long Mountain Roads

Detours Leave Me Ranting

When multiplying or dividing numbers containing decimals by 10, 100, 1000, etc., there's no need for long division or multiplication. You need only MOVE the decimal place.

How many times have you seen something like this ... ?

    2.72

X  100

   0 0 0

0 0 0 0

27200

____________________

This is working hard, not smart.

D.L.M.R tells us that when we divide by 10, 100, 

1000, etc., we move the decimal

left 

and when we multiply, we move the decimal 

right

We move one place for every zero (0) in the 10, 100, 1000, 10,000, etc. 

In the example above, we are multiplying by 100. There are 2 zeroes. We need to move the decimal 2 places to the...............................................right. 

The answer is 272.

More examples, covering some trickier problems, will follow in the next postings.

Multiplication Tables in under 2 minutes - Back by Popular Demand

Can you write out the multiplication table to 10 by 10 in under 2 minutes...

We're nearly up to 1400 hits on this video. I have had all kinds of praise for the content. The video itself was done on a budget of about 59 cents and the "special effects" need upgrading but the ideas are certainly worth sharing. See...

Math Doctor

Multiplication Tables in 2 Minutes

You aren't allowed  to take multiplication tables into a GED exam. But what if there was a strategy that would allow you to write them out once the exam had started? In under 2 minutes, no less. Use the multiplication tables then for multiplying, dividing, putting fractions in lowest terms, finding roots and finding square numbers. In under 2 minutes? Impossible you say. See here for the strategy.

Multiplication Tables

You cannot take your multiplication tables into the GED exam with you. But what if you could write them out on a spare piece of paper in under 2 minutes. See the Math Doctor on Youtube for the solution. He has the prescription.