# Who knows your fractions

Discussion in 'General Chit-Chat' started by Drip Dry, Jul 18, 2012.

1. Maybe I should have paid more attention in elementary school.

How much is 1/5 of say 100.00 --------- 20.00 ? ----- Am I correct ?

=========================================================

Then how much is 4/15ths of 100.00

I'm thinking 100.00 devided by 15 x 4 ======= 26.60 ? Am I correct ?

Even if this is correct, can someone explain an easier way for different numbers

Thanks

Tags:
2. ### 2BModerator   2,685
281
83
May 5, 2011
TX
easiest way is to convert the fract to decimal and then multiply the decimal by the number

1/5 = 0.20 * 100 = 20

4/15 = 0.26666 * 100 = 26.67

3. 26.67 actually, unless I'm wrong here.

4 over 15 = x over 100
cross multiply
15x = 400
divide both sides by 15
x=26.67

same formula every time.... 4. Wow that took me back to algebra class hahaha. I liked math in high school. It was English that had me in summer school lol

5. ### round manActive Member

637
1
0
Oct 16, 2005
back when the gerber 4b was in heavy use i had a fraction to decimal chart taped beside my monitor so I could see at a glance the decimal equivalent of a fraction to enter data to cut graphics in my first version of cadlink(now signlab) which was a 4b emulator for early pc's(286 era) like this one,....http://www.labeldotcom.com/Tips/Fraction-Decimal-Millimeter-Chart.aspx

6. ### GAC05Major Contributor 5,195
469
83
Dec 27, 2005
Guam USA
Set yourself free from fractions - go metric.....

7. Surely you jest...

A base 10 measurement system is rife with fractional results.Since 10 has only three factors, 1, 5, and 2, there's few calculations in that space that won't result in fractional results. Really clumsy fractional results since 10 can only be subdivided easily into 10ths, 5ths and halves.

The reason, or at least one of them, that there's twelve inches in a foot is that 12 has factors, 1, 2, 3, and 4. It can be simply subdivided in to 12ths, 6ths, 4ths, 3rds, and halves. The probability of any calculation yielding an integer result is far more likely than with a base 10 system.

The original question, how is 4/15 of 100 calculated has two primary approaches.

One is to treat is as a ratio as was done in post #3. That would be 4 is to 15 as X is to 100, or restating it as 4/15=x/100. The solve for X. X=4*100/15 or 26.666...

The other is to simply understand the notation. 4/15 means 4 divided by 15. Then the problem is stated 4/15 * 100/1=X. Which actually is a step in solving for X in the ratio statement but doing it this way doesn't require any pesky algebra. Albeit the trivial amount needed to solve the ratio.

Actually the ratio approach is far handier. What if you had an image with an aspect ratio of, say, 23 high by 35 wide and you wanted to reduce the height to 14. What would the new width be? Just state it as a ratio...

35/23=X/14 or 14*35/23

It works the same if you want to make the width, say, 43. What would the new height be?

23/35=X/43 or 43*23/35

Thus endeth the lesson.

8. ### GAC05Major Contributor 5,195
469
83
Dec 27, 2005
Guam USA
I am not sure that I follow you bob.
I must think on this as my math background is the metric equivalent of the North American Standard "zero".

wayne k
guam usa

9. WOW!!! Nice Bob.