La problema de matimatica

Wanna add 10 percent? Just multiply your starting load by 1.1

For 5%, multiply by 1.05

Added:

Of course you should also think about the result. IOW, does it make sense. If you add 10% to a 5.2 grain load, that's .52 grains, is that a larger amount that might not be wise?

If you add 10% to a load, the pressure can go up much more than 10%

to figure percentages from one grain to another (ie. 5.2 gr to 6.2 gr is what %)

6.2 minus 5.5=.7
.7 divided by 5.5 (the smaller of the two above #'s)=.127 or 12.7%

So an increase TO 6.2 FROM 5.5 represents an increase of 12.7%

To double check yourself.
Multiply the 12.7% by the lesser weight 5.5:
.127 Mult by 5.5=.6985 (rounded to the original .7 difference in the two above charges)


To bump a % up, say, 15%:

convert the desired increase to a decimal (move decimal 2 spaces to the left) ie 15% becomes .15 and 5% becomes .05

Multiply your beginning charge of 5 gr. by .15, this total is .75, then add that .75 back to your original charge of 5 gr
So 5 gr bumped up 15% would be 5 gr + .75 gr= 5.75 gr.

To lessen a charge you subtract your figure from the original charge. ie a 15% lesser charge from 5 gr would be 5 minus .75= 4.25 gr.

Yo Pedro, I'd be carefull developing loads using percentages instead of actual weight in grains or tenths of a grain.

HA! A math question. I knew my math degree would be useful for SOMETHING.


Ok, you've asked two questions.

Number One: PERCENT OF CHANGE

If you are trying to figure out what percentage a change in grains is (5.2 grains to 5.3 grains, for example) that is a PERCENT OF CHANGE. The formulas is as follows:

PERCENT OF CHANGE = (New amount - old amount) / old amount

Using the example: 5.2 grains to 5.3 grains

Percent of change = (5.3 - 5.2) / 5.3 = 0.1 / 5.3 = 0.0189 = ~0.02
Roughly a 2% increase.


In reverse: 5.3 grains down to 5.2 grains

Percent of change = (5.2 -5.3) / 5.2 = -0.1 / 5.2 = -0.0192 = ~ -.02
The negative just means it's a decrease this time (obviously), so we see roughly a 2% decrease.


Just make sure to keep track of which is the new amount and which is the new amount. Especially when you divide the difference by the OLD amount. If you use the wrong number it will, of course, throw off your answer.



Number two: PERCENTAGES
Ok, if you want to change the powder weight by 5% or 10% you are dealing with a PERCENTAGE.

PERCENTAGE = (1 +/- the percent of change) * original weight


An increase: 5.2 grains, plus 10%

10% as a decimal is 0.10 (just move the decimal point two places left).

Percentage = (1 + [plus because it's an INCREASE] 0.10) * 5.2 = (1.10) * 5.2 = 5.72


A decrease: 5.2 grains, minus 10%

Once again, 10% is 0.10.

Percentage = (1 - [minus since it's a decrease] 0.10) * 5.2 = (0.90) * 5.2 = 4.68



Hopefully that makes some sense. Feel free to ask for clarification is I did a bad job of explaining it.

PERCENT OF CHANGE = (New amount - old amount) / old amount

Using the example: 5.2 grains to 5.3 grains

Percent of change = (5.3 - 5.2) / 5.3 = 0.1 / 5.3 = 0.0189 = ~0.02
Roughly a 2% increase.


In reverse: 5.3 grains down to 5.2 grains

Percent of change = (5.2 - 5.3) / 5.2 = -0.1 / 5.2 = -0.0192 = ~ -.02
The negative just means it's a decrease this time (obviously), so we see roughly a 2% decrease.


Just make sure to keep track of which is the new amount and which is the new amount. Especially when you divide the difference by the OLD amount. If you use the wrong number it will, of course, throw off your answer.

Phantom Warrior,
Your words are correct but you made the same mistake you warned him about. You divided by the NEW weight instead of the OLD weight.

Examples should be:

Using the example: 5.2 grains to 5.3 grains

Percent of change = [(5.3 - 5.2) / 5.2] x 100 = (0.1 / 5.2) x 100 = 0.0192 x 100 = 1.9%

In reverse: 5.3 grains down to 5.2 grains

Percent of change = [(5.2 -5.3) / 5.3] = (- 0.1 / 5.3) x 100 = - 0.0189 x 100 = - 1.9%

Good shooting and be safe.
LB

I am stricken with remorse. LHB1 is correct. I guess that just goes to show the importance of CHECKING YOUR NUMBERS!

Thank you, Phantom Warrior, for the service and sacrifice you are giving our country. Hurry home...Safely...

Your words are correct but you made the same mistake you warned him about. You divided by the NEW weight instead of the OLD weight.

Click to expand...

I actually noticed that too. I think I went to school for far too long.

Phantom Warrrior, hope all is well over there. I live not far from you over here, just west of Park Rapids. Thank you for your service sir.