Everyday math, grade 4 question

[oceanbaby]

Hi - I'm hoping someone can help me with this. My son is studying mean, median, mode. He gets how to do it, and I understand it, but I have a question about how to solve this kind of problem:

Kids in a class are selling rolls of wrapping paper. The chart shows the number of rolls sold, and how many students. So, 3 students sold 20 rolls, 2 students sold 21 rolls, 5 students sold 22 rolls, 2 students sold 23 rolls, 3 students sold 24 rolls, 6 students sold 26 rolls, zero students sold 26 rolls, and 1 student sold 27 and 28 rolls.

He is supposed to find the median of the number of rolls sold. Is he really supposed to write out:

20 20 20 21 21 22 22 22 22 22 etc., to find the median? Or is there a shortcut that they are teaching to solve this? I looked on the everyday math website and don't see anything about it.

Thanks!

[Fujiko]

Can he just halve the total number of students, and count up to that number on the chart?

It seems simple to my adult brain, but forgive me if it's a little too complicated of a shortcut for a 4th grader.

[velochic]

Originally Posted by oceanbaby

20 20 20 21 21 22 22 22 22 22 etc., to find the median? Or is there a shortcut that they are teaching to solve this? I looked on the everyday math website and don't see anything about it.

Thanks!

Yep, this is exactly how you do it. The middle number of the sequence will be the median.

[VisionaryMom]

If his teacher wants to see his work process, then yes, that's what he needs to do. At least, I've never seen it written out in a different way.

[oceanbaby]

Thank you. The main problem is that heruns out of space along the bottom of his paper writing out all the numbers and goes to a second line and then gets lost as to where he is in the line! I was hoping there was some shortcut way to find it.

[eepster]

Let him write them out using as many lines as he needs. Then use 2 pawns as place holders. Move them along the line one from the beginning and the other from the end towards each other. Move them in sequence and they should meet each other at the median.

[zebra15]

Originally Posted by oceanbaby

Thank you. The main problem is that heruns out of space along the bottom of his paper writing out all the numbers and goes to a second line and then gets lost as to where he is in the line! I was hoping there was some shortcut way to find it.

Oh math in our house uses LOTS of paper. For a problem like this DS would use a seperate sheet of paper and list the numbers from top to bottom
20
20
20
21
21
21
22
22
23
23
23
24.....

For DS its much easier to see the answer and the lines on the paper keep everything neat and orderly.

[TiredX2]

Another option is to do something like this:

Kids in a class are selling rolls of wrapping paper. The chart shows the number of rolls sold, and how many students. So, 3 students sold 20 rolls, 2 students sold 21 rolls, 5 students sold 22 rolls, 2 students sold 23 rolls, 3 students sold 24 rolls, 6 students sold 25 rolls, zero students sold 26 rolls, and 1 student sold 27 and 28 rolls.

20 21 22 23 24 25 - 27 28
x x x x x x
x x x x
x x
x x
x

ETA: Okay, that didn't work--- just picture the xs below each number.

This makes the mode VERY obvious and for the median you can just start crossing off from the beginning and end until you meet in the middle.