my daughter has some maths homework on mean and range within a set of data.
a question is: write a set of 5 weights which have a mean of 7kg and a range of 6kg.
i must be stupid, i don't know how to do this without longwinded hit and miss of trying differnt numbers and cannot find the formula on google.
i'm not after the answer, just how to work it out so i can explain it to my daughter.
can anyone help please?
4,6,7,8,10?
I guess as long as the numbers either side of the mean balance each other out...
edit - I am terrible at maths, and my 9 year old's homework stumps me
Theres an odd number of weights so spread the each side of the required mean with the last one equal to mean.
So eg 5 6 7 8 9
edit - or lots of other combo's
well just add 3 to 7 and subtract three from seven to give your range and then 6, 7 and 8 so it all works out to the desired mean. unless im missing something obvious.
Isn't it 7,8, 9 and 3, 4 and 5. oops 4 5 6 & 8 9 10 double oops 4 5 7 9 10
Mean is average of numbers
Range is the difference between largest and smallest.
Weights are usually round numbers.
aP - that's 6 weights. couldashoulda...don't forget the range, Inigo...you have really baffled me
Think of 5 weights in a row.
Mean of 7 so lets say the 3rd weight (middle one) is 7kg
Range of six so that must mean 1st and 5th are 4kg and 10kg respectively. Then you have 2 logical options for each of the other two so you end up with 4, 5, 7, 9 and 10.
(or 4,6,7,8,10)
couldashoulda...don't forget the range,Doh.
Modifying my explanation then: 4 4 7 10 10.
4,6,7,8,10.
oh hell, even more confused now.
but made it work with 3, 7, 8, 8, 9
Another way of thinking of this is that if it has to be 5 numbers with a mean of 7 then 5x7=35. So then find 5 numbers that add up to 35 and have a range of 6. ..
if desired mean is x and desired range is y then the upper and lower limits are x+(y/2) and x-(y/2) the the rest of the numbers from the middle.
*shakes head in confusion* Maths was never a strong point here.
toys19, yep thats how i ended up working it out.
drama over, back to jarvis cocker's sunday session on i-player (fascinating feature on french punk) whilst spraying mould on the walls with bleach solution. lovely.
that hurts, bound to be essential to know though, if you, erm, want set of 5 weights which have a mean of 7kg and a range of 6kg. I have no conceivable usage for weights such.
Fast forward 8 years to degree level and we still have to do simple things like that.. Just now you call the mean the expectation.
bound to be essential to know
yes, mine was the interior volume of a cone at o-level. 29years on i still have found no reason at all to want to find out the interior volume of a cone.
btw, excellent feature on french punk and situation-ism about 45mins in on cocker's sunday show... http://tinyurl.com/4klcqcl
write a set of 5 weights which have a mean of 7kg
The total of the 5 weights has to add to 35kg
range of 6kg.
The lowest and the highest have to be 6kg apart.
29years on i still have found no reason at all to want to find out the interior volume of a cone.
You're not in the ice cream business then?
no, but once upon a time i did serve mr. whippy ice creams. its surprisingly tricky.
once upon a time i did serve mr. whippy ice creams. its surprisingly tricky.
I'll bet!! If there was one person who didn't need ice cream i would have thought it was him!
Surely at age 11 she isn't supposed to get help from parents with homework, she should be asking the teacher? The whole point of this is so that her teacher can gauge effectively where her strong and weak points are. Plus, how do you know our explanation/methodology will match that used in the curriculum?
Surely kg is a measure of mass. Weights would be Nm?
So unanswerable.
Surely kg is a measure of mass. Weights would be Nm?So unanswerable.
What's worse than an internet pedant? An internet pendant that's wrong.
Its N, not Nm. Silly.
To me it looks like most if not all have gone for MEDIAN rather than the mean..
4+6+7+8+10 = 35
Mean = 35/5 = 7
Range = 10-4 = 6
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