# A 5th grade math question...

Discussion in 'Elementary Education' started by Major, Feb 22, 2009.

1. ### MajorConnoisseur

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Feb 22, 2009

I subbed for a 5th grade class recently. During math they were given this problem:

80% of a number is 60. What is the number?

I was very surprised to find only a small number of kids knew the answer.

So for you elementary teachers out there is this a 3rd, 4th, 5th or 6th grade level problem?

Major.......

3. ### AliceaccMultitudinous

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Feb 22, 2009

I'm not elementary.

But as soon as they can cross multiply, they can handle "is over of..."

4. ### czaczaMultitudinous

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Feb 22, 2009

It's definitely not 3rd grade. I'm second grade and the kids don't know percentages when they leave me... I was taught that 'of' in such a problem could be substituted with a multiplication sign...so
80% of a number is 60 would call on me to say .80 times 'x' = 60...Then I'd divide 60 by .80= 75....Not bad!!

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Feb 22, 2009

We do that in 6th grade - but they may do it in 5th as well. I like czacza's way... we talk about multiplication meaning "of" as well.

6. ### MajorConnoisseur

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Feb 22, 2009

I guess I thought the problem would be quite simple for 5th graders...... but I was wrong.

My problem is I don't know what math concepts kids "should" know by the time they are in the 4th, 5th, or 6th grade.

Major...

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Feb 22, 2009

I've taught 5th and 6th and it is definitely covered in more detail in the latter....Even then, many students still struggle with percentages of a number. We taught it both ways, using multiplication in the place of "of" and using the part/whole (is/of) relationship. It was definitely a tricky chapter for lots of kids. They really have to be able to deconstruct the problem and figure out which numbers to use where.

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Feb 22, 2009

I recently taught 6th grade math and many of the students did not know "of" meant to multiply.

9. ### ms_teacherCompanion

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Feb 22, 2009

I am a 5th grade teacher in NYC. Everyday Math covers this late in the school year in 5th grade. I would not expect 5th graders to know this at this point. Def. more of a 6th grade topic.

10. ### shouldbeasleepEnthusiast

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Feb 22, 2009

Introduced here, but def. not mastered. I'll give it to my kids tomorrow as a warm-up and see what they do. The majority will freeze, but I may have 4 or 5 who figure it out this way...
(since we have a tendency to set up equations in this class)

.80 X n = 60

Move the decimal twice and add two zeroes to the 60

80 X n = 6000

n = 6000 (move this 80 over to under the 6000, it won't go)
80

6000 divided by 80 = 600 div. by 8 =

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Feb 23, 2009

Percent is not discussed by now in fifth grade in AL. It is definitely the last part of the year topic....

12. ### mmswmModerator

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Feb 23, 2009

If you were doing it in 5th grade, it was most likely just introduced to them

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Feb 23, 2009

It wouldn't be typical for a 5th grade class. They just mastered addition of fractions and mixed numbers and have started multiplying fractions this month. We work on fraction, decimal, and percent equivalents in calendar each morning, in a limited way. 6th and 7th work on using percentages in algebraic equations.

14. ### MajorConnoisseur

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Feb 23, 2009

Thanks everyone........

15. ### knitter63Groupie

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Feb 23, 2009

You are right, EDM does cover late in the 5th grade year. Unfortunately, the achievement test we take has several of these types of problems on them. I am forever reinforcing that "of" means to multiply-and we set it up as fractions. (yes, I know they will have to divide, too, but believe me, they can use the practice in that as well!!!!)

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