Perplexing math

[mjoekingz28]

I just cant fathom why!

So, i have 100 of something and add 50%,. I now have 150. But if I take 50% from 150 I now have 75.


I had it more clearly in my mind earlier, but this is the best scenario I can put together at this moment.

 

[jorton]

take away 1/3 to get back to 100

 

[Nick1994]

Originally Posted By: mjoekingz28
I just cant fathom why!

So, i have 100 of something and add 50%,. I now have 150. But if I take 50% from 150 I now have 75.


I had it more clearly in my mind earlier, but this is the best scenario I can put together at this moment.
Sounds fine to me, what's the problem with it?

 

[JHZR2]

because % is per cent, where cent means hundred. Think pennies, one hundred cents to a dollar.

One per cent, one per one hundred.

So if you have 50 per cent, then you have fifty per hundred. So 50% of 100 is 50 per one hundred or 50 somethings.

If you have 150 somethings, then you have 100 and an additional 50. 50% of the first 100 is 50, but remember, this is per cent or per 100. You actually have 1.5 one-hundreds... So you need to take the 50% of the other 50, which is 25 somethings.

Add them together and you get 50+25=75.


No different than if you have 1000 somethings. It is per one hundred, so a thousand is ten one hundreds. So 50% (per one hundred) of 1000 means you take 50 from the first 100, 50 from the second 100, and so on.

Eventually youll have ten groups of 50. Ten groups of fifty if added/multiplied is five hundred.

And so on.

 

[Pop_Rivit]

Originally Posted By: mjoekingz28
I just cant fathom why!

So, i have 100 of something and add 50%,. I now have 150. But if I take 50% from 150 I now have 75.


I had it more clearly in my mind earlier, but this is the best scenario I can put together at this moment.


Perplexing? Not really. 50% of 100 is 50. Therefore you end up with 150 when you add 100 and 50.
50% of 150 is 75, so if you subtract 75 from 150 you end up with 75.

That's the sort of thing we learned in 3rd or 4th grade. Does the current educational system no longer teach simple math?

 

[EdwardC]

Think of it this way, you have 100, you multiply by 150% (1.5) to get 150. Divide 150 by 150% (1.5) to get back to 100.

 

[Warstud]

Originally Posted By: Pop_Rivit

That's the sort of thing we learned in 3rd or 4th grade.

Yeah Right.

 

[JHZR2]

Originally Posted By: Warstud
Originally Posted By: Pop_Rivit

That's the sort of thing we learned in 3rd or 4th grade.

Yeah Right.


I dont know about percentages, but I recall doing groups of items that one would count (it was groups of beads on strings), before kindergarten.

They would become in the third grade, "times tables" effectively. But we were counting this way in pre-K.

 

[bvance554]

3 guys chip in for a motel room that costs $30. Each pay $10. The clerk realized she made a mistake and the room is only $25. Since she can't split $5 evenly 3 ways she puts $2 in her pocket and gives each of the 3 guys $1. That leaves each of the 3 guys paying $9 apiece. 3 x $9 = $27. $27 plus the $2 the clerk pocketed = $29. What happened to the other $1? We started off with $30.

 

[CarbonSteel]

An old one and a bit of sleight of hand. They paid $9.3333333333 each. $25/3 = $8.333333333 + $1.00 = $9.33333333 x 3 = $28.00 + $2.00 = $30

 

[JHZR2]

Originally Posted By: bvance554
3 guys chip in for a motel room that costs $30. Each pay $10. The clerk realized she made a mistake and the room is only $25. Since she can't split $5 evenly 3 ways she puts $2 in her pocket and gives each of the 3 guys $1. That leaves each of the 3 guys paying $9 apiece. 3 x $9 = $27. $27 plus the $2 the clerk pocketed = $29. What happened to the other $1? We started off with $30.


$25 room charge, $3 refund, and $2 tip to the owner. I dont get what's wrong besides the wording... The guys didnt pay $27, they paid $25 for the room.

 

[shanneba]

Originally Posted By: bvance554
3 guys chip in for a motel room that costs $30. Each pay $10. The clerk realized she made a mistake and the room is only $25. Since she can't split $5 evenly 3 ways she puts $2 in her pocket and gives each of the 3 guys $1. That leaves each of the 3 guys paying $9 apiece. 3 x $9 = $27. $27 plus the $2 the clerk pocketed = $29. What happened to the other $1? We started off with $30.


They each paid $9 ($10 - $1) 3 x 9 = $27 MINUS the $2 the clerk kept = $25

 

[UncleS2]

Percent does not stand alone. In practical use, you have a percentage of *something*.
It would be strange indeed if 50% of 100 was the same thing as 50% of 150.
Repeat- you have a percentage of *something*.
Yeesh.

 

[OneEyeJack]

Here's one for you business people. You buy a product for $12 and mark it up 40%. What's the selling price. Is it 12x1.4 for $16.80. That's what a lot of people do and it's wrong.

If you mark up a $12.00 item 40% then it's retail selling price is $20.00. Now if you discount it 20% for a wholesale deal to another business you'd sell it for $16.00 leaving 20% profit for you, or $4.00 and the other business can sell it for $20.00.

In other words, to mark up a $12.00 item 40% you would multiply 12x1.6667 and get 20.00, not 1.4. The percentage is based on the retail selling price. If it's not you'll have a real adventure figuring out your books at the end of the year.

 

[Shannow]

OneEyeJack, that's Gross Margin, not mark-up.

It's $12/(1-40%)

40% mark up is $12*(1+40%)

 

[Garak]

Think of percentages as fractions and note the relationship between division and multiplication. Dividing something by 1/2 is the same as multiplying it by two, and dividing something by 2 is multiplying it by 1/2.

 

[bvance554]

Originally Posted By: 2010_FX4
An old one and a bit of sleight of hand.


It is old, and slight of hand, but still fun to me because I had a college algebra teacher throw chalk and pronounce it was 'unsolveable' after spending 10 minutes scribbling on the board 20 years ago.

 

[Trajan]

Originally Posted By: mjoekingz28
I just cant fathom why!

So, i have 100 of something and add 50%,. I now have 150. But if I take 50% from 150 I now have 75.


I had it more clearly in my mind earlier, but this is the best scenario I can put together at this moment.


What's hard to fathom is high school students who can't tell you what 6% sales tax on a dollar is.

 

[Johnny2Bad]

% up and % down are not equal.

If you ever work retail or wholesale and have authority or insight on pricing, you figure it out pretty quick.

You buy an item for $80, and mark it up 50% = $120 retail.

Your retail markup is 50%; (120/80) your gross profit margin is 33% (80/120).

 

[Garak]

Walmart Canada and Canadian Tire do it very easily on oil. Their retail markup is 100%.