dividing by decimals?

2008-06-10 6:08 am
12.5/.025
the answer is 500 but how do you find that out without a calculator

回答 (7)

2008-06-10 6:12 am
✔ 最佳答案
Move the decimal points 3 places to the right in both the numerator and denominator so you only have integers. 12.5 becomes 12500 while .025 becomes 25.

12500
---------
25

Now it is a simple division:
........ 500
25) 12500

Answer:
500
2008-06-10 6:13 am
Look at the smallest number, which is .025

You want to multiply to take that out of decimal, and since it is in thousands, you will multiply top and bottom by 1000.

(12.5*1000)/(.025*1000) = 12500/25 = 500
2008-06-10 6:12 am
12.5/.025 is the same as
12500/25

I know that 125/25 = 5 (5 quarters in a dollar and 25 cents, etc).
Then just tack on the two 0's to get 500.
2008-06-10 6:19 am
Depends how good you are with arithmetic.

The usual way is to move the decimal point enough places to mean you can ignore them.

12.5/.025 is the same as 125/.25 (decimal place has been moved one place),

which is the same as 1250/2.5 (d.p. has moved 2 places) and that's the same as

12500/25 so now you don't need a calculator (maybe).

4 lots of 25 make 100 so 500 lots of 25 make 12500.

Sometimes, the decimal number allows a few shortcuts. For example this one (after 1 move of the point) became 0.25 or 1/4. That's a nice easy fraction. I know 4 of them make 1 so 500 of them make 125.
2008-06-10 7:19 am
12.5 = 125 x 10^-1
0.025 = 25 x 10^-3

Step-1 : dividing 125 by 25 we get 5
Step-2 : dividing 10^-1 by 10^-3 we get 10^2 i.e 100
Step-3 : Step-1 x Step-2 = 5x100 = 500

For quick, correct & mental calculation, above method appears to be most easy.
2008-06-10 6:14 am
You have to multiply both numbers with 1000 (that is because tge divisor has 3 digits after decimal point, and you have to divide without decimal poin t, if you understand what I mean)
So you will have
12500/25=2500/5=500
I hope you understand - my English is not good enough to explain it better!
anyway - good luck!
2008-06-10 6:16 am
12.5/0.25
= (100/100)(12.5/0.25)
= (12.5 x 100)/(0.25 x 100)
= 1250/25
= 500


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