Curious to see your opinion.

[Steven G]

I was told that an algebra student should not know how to do this problem in their head. 98*5 + 2*5
What are your thoughts? (and Dennis please refrain from saying 500 is your thought)

 

[ksdhart]

Er... why wouldn't an algebra student be able to solve this problem in their head? Surely an algebra student could tell you that 98 of something plus 2 more of the same something is 100 of that something, right? My opinion is that whoever told you that is full of (insert expletive here).

 

[Steven G]

Er... why wouldn't an algebra student be able to solve this problem in their head? Surely an algebra student could tell you that 98 of something plus 2 more of the same something is 100 of that something, right? My opinion is that whoever told you that is full of (insert expletive here).

Do not be so sure that they could do this problem. Having said that I think that they should be able to! A math ed person told me that this was clearly a calculator problem!

 

[Deleted member 4993]

Do not be so sure that they could do this problem. Having said that I think that they should be able to! A math ed person told me that this was clearly a calculator problem!

I suppose that Math-ed person forgot to add - for Idiots!!

i.e.

this was clearly a calculator problem - for idiots.

After saying that - I have to tell you my experience!!

I teach basic engineering here at a community college.

Some of my "so called good-students" got totally frazzled - when I said that I'll take-off 10 points if somebody touched calculator to multiply 7.5 by 12 (convert 7.5' to inches). Not in their head - with pencil and paper - they could not do it properly.

I was so disappointed - and I said something that was not very nice. I said - "you know I have a six-year old grand son and if I prompt him correctly - he would be able to do this in his head!!"

 

[Ishuda]

I was told that an algebra student should not know how to do this problem in their head. 98*5 + 2*5
What are your thoughts? (and Dennis please refrain from saying 500 is your thought)

Now actually I multiplied 98 times 5 (=980/2) and added the 10 (I sometimes forget that important rule about read the complete problem before trying to solve it). I think that may be why the math ed person said it was a calculator problem.

Given that, I think it would be nice if everyone had that bunch of short cuts memorized, things like
-times 5 is times 10 divided by 2
-divide by 5 is times 2 shift the decimal point [divided by 10]
-divide by 4 is divide by 2 twice
-square a two digit number ending in 5 is take the first times one plus itself and tack on 25: 25 * 25 is 2*3 tack on 25 = 625
-apply (a-b)(a+b) = a²-b²: 28*32=(30 - 2)(30 + 2): 3 times 3 (hundred) subtract 2*2 gives 896
and others
I can remember reading a science fiction book way back when (I think pre-teens) who worked a lot of those kind of things into a story. I've even re-read it a couple of times.

 

[Steven G]

What's your point, Jomo?

I just wanted to make sure that I was not being unreasonable thinking that students should know this w/o a calculator. This math ed person has a PhD in math ed and teaches full-time at a community college but teaches only arithmetic because algebra is too hard for him. Simply amazing.

I am glad that most of you agree that a student should be able to handle this.
I have always been amused at how high school teachers and most adjuncts teach a topic and then they never use it again.

They spend time teaching additive inverses but the very next class when they have to solve 3+x=0 they subtract 3 from both sides. Or they show that (x+y)^2 = x^2 +2xy +y^2 but can't 'see' that they can use this to calculate 32^2 as 900 + 120 + 9. These math ed folks pick math ed as their major (they even get PhDs in it!) yet they have no love of math or even any talent in it. I may not know the most advance math but my true love is math and I have mathematical talent. My degrees were in math--why? Because I wanted to know math and teach it. Not this bs math ed degree.

 

[Deleted member 4993]

I just wanted to make sure that I was not being unreasonable thinking that students should know this w/o a calculator. This math ed person has a PhD in math ed and teaches full-time at a community college but teaches only arithmetic because algebra is too hard for him. Simply amazing.

I am glad that most of you agree that a student should be able to handle this.
I have always been amused at how high school teachers and most adjuncts teach a topic and then they never use it again.

They spend time teaching additive inverses but the very next class when they have to solve 3+x=0 they subtract 3 from both sides. Or they show that (x+y)^2 = x^2 +2xy +y^2 but can't 'see' that they can use this to calculate 32^2 as 900 + 120 + 9. These math ed folks pick math ed as their major (they even get PhDs in it!) yet they have no love of math or even any talent in it. I may not know the most advance math but my true love is math and I have mathematical talent. My degrees were in math--why? Because I wanted to know math and teach it. Not this bs math ed degree.

How did you get that??! :grin::grin::grin: