OT: Simple Math Question

[yesrutgers01]

If it is truly:
-3 and 2/7 , divided by: 1 and 1/4, then the answer is:
-23/7 / 5/4 = -23/7 * 4/5 = -115/35 * 28/35 = -3220/1225 = -644/245

From some of the examples my niece has finally admitted to having as a guide...
After getting the -23/7 * 4/5
They are not converting to decimal but need to keep it as a fraction. If I go by the example in her guide it would be -92/35
but I am not even sure about that. lol Glad I have to deal with how to pay my mortgage and save for retirement and not 7th grade math...hahaha Need to give her back to her mom soon or I will go grey. I can't get a bit of work done as she has such bad habits.

 

[PiscatawayMike]

 

[LC-88]

QED = Quite Easily Done

 

[RU848789]

OK, so, my Niece is staying with us for a while and taking pre algebra - She has a number of fraction equations to do and when she does them, it just isn't computing in my old mind and she can't walk through the steps and seems she is just giving answers she was giving- BTW- her teachers are doing that a lot. Giving quizzes and answers

-3 2/7 divided by 1 1/4 = 23/798

Is this actually the correct answer and how do you get to that answer?

I get -92/77, I'll try to explain:

-3 2/7 equals -23/7

-23/7 divided by 11/4 OR -23/7 times 4/11

multiply across numerator and denominator I get -92/77, not sure if it's right

CJ is correct if it's actually 11/4 (or 2 and 3/4) and not 1 and 1/4 - hard to tell from the way it was typed. If it's -3 and 2/7 divided by 1 and 1/4, instead, then it's -23/7 divided by 5/4, which is simply (-23 x 4) divided by (7 x 5) = -92/35. Any answer in decimal form will be marked wrong as the idea is to understand fractions not decimals.

 

[mikebal9]

So this is wrong?



Convert to decimal

-3 2/7 divided by 1 1/4 =

2/7 = .2857

1/4 = .25

-3.2857 / 1.25 = -2.6285

I always allow my students to work in fractions or decimals, whichever they're comfortable with.

 

[Colbert17!]

Anyone here ever hear of a calculator.

 

[Jersey Boys]

The answer is... four?

 

[RU Golfer]

From some of the examples my niece has finally admitted to having as a guide...
After getting the -23/7 * 4/5
They are not converting to decimal but need to keep it as a fraction. If I go by the example in her guide it would be -92/35
but I am not even sure about that. lol Glad I have to deal with how to pay my mortgage and save for retirement and not 7th grade math...hahaha Need to give her back to her mom soon or I will go grey. I can't get a bit of work done as she has such bad habits.

this quote is the correct answer. when dividing mixed numbers you change them to improper fractions.

-23/7 divided by 5/4

since there is no "real" division in fractions you need to flip the second number and multiply across.

-23/7 * 4/5

at this point you would cross cancel if you could (cant in this case) so just do the math

-23/7 * 4/5 = -92/35

 

[RUBOB72]

-((3x7)+2)/7 * 4/5 (reciprocal of 5/4) =

-23/7 * 4/5 =

-92/35 =

-2 22/35

Exactly... old school math 4-5th grade ( ‘59-60)

 

[RUsince52]

Same method the NCAA used to determine a TD. They never really review the video. We know how this ends up versus the obvious.

 

[RUnTeX]

It's been about 35-40 years for me but this should be about 5th grade level math at the latest, it's just operations using fractions. Not sure how this is pre-algebra, unless it's pre-pre-algebra lol, to make it sound further along than it is. It should be considered remedial, or at best a refresher, for average middle school or junior high students but that's where math education is these days it seems.

 

[yesrutgers01]

It's been about 35-40 years for me but this should be about 5th grade level math at the latest, it's just operations using fractions. Not sure how this is pre-algebra, unless it's pre-pre-algebra lol, to make it sound further along than it is. It should be considered remedial, or at best a refresher, for average middle school or junior high students but that's where math education is these days it seems.

7th grade but admittingly, her public school system is not the greatest. From what I have seen in two weeks is that the teachers are lazy as Fvk.

 

[yesrutgers01]

Thank you everyone. -92/35 was the proper answer.
After the refresher from some of you, it made the rest of the problems fast and easy.

 

[lne001]

Not sure how this is pre-algebra, unless it's pre-pre-algebra lol, to make it sound further along than it is.

I was wondering that very point as well. I would think this is just a refresher on the processing rules for fractions, as algebraic fractions are numerous and are handled the same way as arithmetic fractions.

 

[robcac26]

No offense but it always blows my mind how bad older people are at elementary math as well as spelling and grammar. It seems most of the people chiming in on this thread here got the wrong answer.

If it is truly:
-3 and 2/7 , divided by: 1 and 1/4, then the answer is:
-23/7 / 5/4 = -23/7 * 4/5 = -115/35 * 28/35 = -3220/1225 = -644/245

Technically that is the right answer once you reduce that fraction down to -92/35, but as someone else previously mentioned, you don't need a common denominator to multiply or divide, only to add and subtract.

So this is wrong?



Convert to decimal

-3 2/7 divided by 1 1/4 =

2/7 = .2857

1/4 = .25

-3.2857 / 1.25 = -2.6285

I always allow my students to work in fractions or decimals, whichever they're comfortable with.

The problem with that is that you don't get as exact of a number as a fraction would be since you have to arbitrarily decide how many decimal places you're going to use, and that decision results in slightly different answers because it reduces the number of possible denominators. As seen above, Tango Two decided to only use four decimal places. 2/7 converted to a decimal has over 15 decimal places, cutting off the rest and then converting back to a fraction at the end results in a different fraction than if you used more decimal places, which is why he ended up with -2 5/8 instead of -2 22/35.