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Apparently anyone with a solid understand of a math problem such as 52-27 would approach the problem like this:

Start at 27

27+3=30

30+20= 50

50+2= 52

3+2+20= 25

Ok am I the only one thinking that that's horse poop?

I'm not great with math and I admit that but this is my approach:

52-27

12-7=5

40-20=20

20+5=25

My husband who is an engineer said that he would Solve 52-27 like this:

52-7=45

45-20=25

We both find the above way very long and has unnecessary steps.

The reason I ask is because on another board the teacher said that this was the method that people with strong math concepts use to figure out problems in their head.

Also I see this frequently as CC aligned or how the CC says to figure out these problems. To me all those steps are confusing. I dunno... I just don't get it.





 



 


 

by on Mar. 11, 2014 at 1:03 AM
Replies (11-20):
Chasing3
by Bronze Member on Mar. 11, 2014 at 3:53 PM

i solve it like this:

counting on my fingers: 28, 29, 30 (I'm holding up 3 fingers so I don't forget)

then counting in my head: 40, 50 (try to remember 20 here)

then on my fingers again: 51, 52 (now I"m holding up 5 fingers)

SO my answer is 25.


(I should also admit I can't even read through your examples and get it, without very intesne concentration on my part! I just glossed over that part and solved it my own way)!!


kirbymom
by Sonja on Mar. 11, 2014 at 6:36 PM
Does anyone take 1 away from the 5 making it 4 and adding the 1 to the 2 and then solve the problem this way or is that too old fashioned nowadays?
Mommy2Phenley
by Bronze Member on Mar. 11, 2014 at 8:45 PM
My method:

52 is only two more than 50
27 is two more than 25
50-25=25
I don't think through the first two steps I just see it. So I come to the answer almost as quickly as I look at it.
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SarahNElijah
by Member on Mar. 11, 2014 at 8:54 PM
I think the actual truth is that anyone with strong math skills uses rounding/number manipulation to be able to answer a problem like that in their head.. In other words, all three of those examples simplify the numbers to make solving simple without paper, so all three are correct in my mind. I would mostly do it the way your DH did in his head though.
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mem82
by Platinum Member on Mar. 11, 2014 at 9:16 PM

I actually do Math the first way but I do teach me kids the traditional way. LOL

awesomemommy2
by on Mar. 11, 2014 at 9:21 PM
Its easier to count up (or add) than subtract which is why they teach the first way and not yours which are both the same number of steps. The other way and my opinion on the easiest is;
52-30=22
22+3=25
Larger whole number less the smaller number rounded to the nearest ten and then either add or subtract the difference from the rounding.
awesomemommy2
by on Mar. 11, 2014 at 9:25 PM
The funny thing is that what you did is the methodology in the first way. Adding up.
3 to 30
20 to 50
(Now at 23)
And then 2 more
Answer= 25

Quoting Chasing3:

i solve it like this:

counting on my fingers: 28, 29, 30 (I'm holding up 3 fingers so I don't forget)

then counting in my head: 40, 50 (try to remember 20 here)

then on my fingers again: 51, 52 (now I"m holding up 5 fingers)

SO my answer is 25.

(I should also admit I can't even read through your examples and get it, without very intesne concentration on my part! I just glossed over that part and solved it my own way)!!

katyq
by Member on Mar. 11, 2014 at 10:43 PM

Close the gap, however works best in your own mind :p

AshleyLynnW
by Member on Mar. 11, 2014 at 11:02 PM
I figured it out this way too!

Quoting paganbaby:

I counted by 10's starting with 27- 37, 47 (that's 20) then 48, 49, 50 , 51, 52 (that's 4) So the answer would be 24.

Edit I meant 5! I Haven't had my coffee yet,lol.

paganbaby
by Silver Member on Mar. 11, 2014 at 11:09 PM
1 mom liked this

Great minds think alike,lol.

Quoting AshleyLynnW: I figured it out this way too!
Quoting paganbaby:

I counted by 10's starting with 27- 37, 47 (that's 20) then 48, 49, 50 , 51, 52 (that's 4) So the answer would be 24.

Edit I meant 5! I Haven't had my coffee yet,lol.





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