Help please with DD's 4th grade math...."Broken Calculator??"

[Lisa L from MI]

I have never heard of this...and tried to find it on the net...found some stuff but not these kinds of problems....can anyone help and show me the steps????

SOLVE EACH OPEN SENTENCE ON YOUR CALCULATOR WITHOUT USING THE "BROKEN" KEY. RECORD EACH STEP.

1) Broken Key: -
To Solve: 68 + X = 413

2) Broken Key: X
To Solve: W/15=8



I am assuming you have to solve for the X in number one and the w in number 2.......I was a wiz at math in my days....but this seems absolutely stupid to me.........

Thanks for any help!!!!!!

 

[Pin Wizard]

I suppose they have to find a different way to solve it other than subtracting the first and multiplying the second. If my keys were broken, I'd resort to pencil and paper!

 

[Lisa L from MI]

I think that too......I just think this seems awfully confusing.....especially for a 4th grader!!

 

[#1 Disney Fan]

Oh okay, I understand. So as Pin Wizard was saying, you can't use subtraction in the first one, or multiplication in the second.

Here's the trick for the second one: Since you can't use multiplication... try using division using the reciprical of the number. For instance... if you want to multiply 5 x 5... but you can't use multiplication... try.... 5 (divided by) 1/5. That's the same thing as 5 x 5.

So, for the second one.... w/15 = 8. Normally you'd multiply 15 x 8 to get w=120.. But... you can't use multiplication. So, use the reciprical division. w = 8 divided by 1/15 = 120. Ta da!

Now... back to my own school work so I don't have to pull a total all-nighter. Hope this helped though!

 

[ErikdaRed]

Its an estimating exercise. Make a guess at the answer, then check yourself with the calculator. Iterate to the correct answer.

 

[Lisa L from MI]

It did help....me!!!......BUT....for a 9 year old??? They just started learning long division and jump to this???.......Why not do it the old fashion way??!!......I just asked her if she heard of a reciprical....and she never even heard of the word!!!

Well, I think I will just write the teacher a note tomorrow...maybe he can call me and explain it...

thanks for your help guys!!

 

[d.kurz]

Sounds like the Everyday Math program out of the Univ of Chicago!! Teachers will NOT be happy if you teach them "your" way!! I specifically remember the broken calculator exercises! How about "in and out boxes?"

Good luck!

 

[Lisa L from MI]

Dorothy...it is Everyday math from Chicago!!! I caught on to the in out thingy...but this is really ridiculous I think!!!!

 

[#1 Disney Fan]

Ok, so here's what I don't understand with all these new math techniques. The last one I heard about was that new "grid" form of multiplication. What are these kids supposed to do when they get to University? Draw grids at the side of their page to do multiplication on exams??? It doesn't seem practical, but that is JHMO and I don't know a lot about all this "new math." (Calculus... I've taken about 6 courses in... my "elementary school new math" not a clue, LOL ) Maybe it's more practical than what it seems, but that's just my initial opinion.

Good luck!

 

[Lisa L from MI]

The long division is crazy!!! Even some of the 3 or more digit addition was, and still is!!!.....But you know, DD can just "whiz" through an addition problem written out next to eachother......for example...3428 + 6239....It just amazed me!! So, maybe it does work....how, I don't know.

Dorothy...I will pm you back tomorrow after I talk to the teacher.....

 

[damo]

Looks like a simple trial and error question, or guess and check as they say in many systems. This is a typical grade 4 question to get kids to find other ways of solving a problem. Just keep plugging numbers into the calculator until the equation works. You're lucky they are letting you use a calculator. Most times questions like this are done in the numbers and numeration section and kids aren't allowed to use their calculators. At this age, the kids don't know how to solve equations yet to they simply need to substitute numbers until the equation is solved.

 

[worm761]

for the first one use a negative number. if you add -68 to each side it would be the same as subtracing.

60+x+(-68)=413+(-68)

 

[jfulcer]

You could always do:

413 M+
68 M-
MR

There's your answer!