Dividing Decimals

[FrkyBgStok]

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I have troubles multiplying decimals but I need a hand figuring out a quick and easy way to divide decimals. Like concentrations. For example, .0015/.25. is there a quick way that you guys can look and say, "hey, that's .006?" This is killing my score.

 

[eldoctor]

you have to put things in scientific notation:

0.0006/0.00072 = 6x10^-4/ 72x10^-5

then divide by common denominator (ie 6)

and you get

(1/12)x10^1.

You should know that 1/12 is ~ 8x10^-2

so the final answer is 8x10^-1 or 0.8

 

[DougTPR]

I have troubles multiplying decimals but I need a hand figuring out a quick and easy way to divide decimals. Like concentrations. For example, .0015/.25. is there a quick way that you guys can look and say, "hey, that's .006?" This is killing my score.

When I teach TPR classes one of the tricks I always use is the method of magic fractions...

Look for fractions as they are easier to work with quickly.

0.0015/0.25 = 0.0015 / (1/4) = 4 * 0.0015 = 0.006

Applying the rules of multiplying by inverses takes care of the problem of dividing by a fraction.

Hope this helps.

 

[FrkyBgStok]

Hm....I will be honest, your methods confused me. But I figured it out for simplicity using the scientific notation.

.0015= 150x10^-5
.25= 25x10^-2
150/25 is 6. Do the exponents and its 6x10^-3. BAM

Thanks for the insight.

 

[Entadus]

You double posted... I answered your other thread with the scientific notation suggestion. Good luck!

 

[BerkReviewTeach]

I have troubles multiplying decimals but I need a hand figuring out a quick and easy way to divide decimals. Like concentrations. For example, .0015/.25. is there a quick way that you guys can look and say, "hey, that's .006?" This is killing my score.

Aim to get an easy denominator! In your example, the easy denominator would be 1.

If you multiply both numerator and denominator by 4, it becomes an easy denominator.

0.0015/.25 = (4 x 0.0015)/(4 x 0.25) = 0.0060/1 = 0.006.