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A question for maths teachers and anyone who is interested- My Maths niggle

(16 Posts)
bruffin Sun 11-Oct-09 14:45:54

Both DCs Yr7 and YR9 sometimes get homework on My Maths

Why when it asks for the answers rounded to 1 decimal place does it always round down?

ie DD had a question to work out the surface area of a tube the answer the decimal part of the answer was *.197 (can't remember the * bit) so DD rounded it up to .2. My Maths marked it wrong and said the answer was *.1

Both DH and I feel the answer should be .2.

The question definitely says round to 1 decimal place, not round down to 1 decimal place.

notanidea Sun 11-Oct-09 16:12:28

I am not a maths teacher but asked DB who is an engineer and done advenace maths.
Depends on what the question was- if the question is to round up it has to 0.2 and if it was to round down then it is 0.1. If nothing was specified but said to give a rounded number - then anything above 0.15 would be 0.2 and anything below is 0.15 would be 0.1

Hope this is of some use to you.

notanidea Sun 11-Oct-09 16:13:25

In other words - you are right

juuule Sun 11-Oct-09 16:15:27

Does it ask for it to be rounded? Or does it just say to give the answer to 1dp?
If it does ask for it to be rounded then I agree with bruffin.

juuule Sun 11-Oct-09 16:20:29

Sorry that should be agree with notanideablush

lottiebunny Sun 11-Oct-09 16:22:32

I agree with you. I am not a maths teacher but I am doing a masters in maths. Rounding means you round to the nearest number.

.1 would only be the answer if it was being rounded down.

NormaStanleyFletcher Sun 11-Oct-09 16:26:11

Agree with the others. Only if rounding down is specified would it be .1

bruffin Sun 11-Oct-09 16:49:49

You have made me think now, will have to look again. So if it just says to 1 decimal point it should be cut off after the first point.

But I don't understand really why it asks for that rather than rounding which would be more accurate

lottiebunny Sun 11-Oct-09 17:00:37

IMO, if asked to give an answer to 1dp I would round to 1dp.

juuule Sun 11-Oct-09 17:07:34

Bruffin, I'd check again.
I wouldn't be surprised if it just wanted it to cut off after the 1dp.

Niecie Sun 11-Oct-09 17:11:36

Does it say round or does it say give the answer correct to one decimal place?

If the word round is not there then just chop off the rest of the answer but if it does say round then, like everybody else says the answer My Maths gives is wrong!

lottiebunny Sun 11-Oct-09 17:34:46

I disagree with just chopping off the rest of the answer if it does not say round. Giving an answer to a certain number of decimal places (or alternatively significant figures) implies rounding.

juuule Sun 11-Oct-09 17:40:17

Lottie I think that's the way it's done though at ks3 if rounding isn't mentioned.

bloss Sun 11-Oct-09 17:46:06

Message withdrawn

Niecie Sun 11-Oct-09 18:25:32

Lottie, I am not saying it would be right to chop off the end, I am just saying that might have been their thinking. I would automatically round up too, wouldn't even think there was an alternative but there has to be some reasoning behind the software.

bloss reasoning sounds OK as well but the question was about tubes so probably not the reason in this case.

lottiebunny Sun 11-Oct-09 18:30:15

The reasoning behind the software is probably just lazy programming grin

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