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 Post subject: maths helpPosted: Sun Oct 15, 2006 10:01 am
Hi
I need urgent help withindex form problems such as
The mass of a neutron is 1.6725x10-24g electron 9.109x10-28g proton 1.6748x10-24g

An atom of carbon is made up of 6 neutrons 6 protons and 6 electrons

Q1)what is the mass of one at of carbon? IS IT AS SIMPLE AS 75.17 x10-456g

Q2)How many atoms of varbon are there in 1 gram of carbon

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 Post subject: Posted: Sun Oct 15, 2006 12:18 pm

Joined: Fri Mar 17, 2006 5:12 pm
Posts: 1300
Location: Birmingham
Hi Kate,

No I'm afraid you can't just add the indices together like that.

What you need to do is as follows:

1. Firstly, choose a common index factor, 10-24 is the best in this case.

2. Convert all of the elementary particle weights to the same factor 10-24. In this case this just means dividing the Electron numerator by 10,000. Hence 9.109 x 10-28 = 9.109 div 10,000 (x 10-24)=

0.0009109 x 10-24g

3. Then you can add the various particle weight components together:-

3 (a) 6 neutrons = 10.035 x 10-24
3 (b) 6 protons = 10.0488 x 10-24
3 (c) 6 electrons = 0.0054654 x 10-24

Therefore:-

Q1 The mass of one atom of carbon is 20.0892654 x 10-24grams

Q2 To work out who many atoms of carbon there are in 1 g you divide 1 by the answer to Q1 above:-

1 div ( 20.0892654 x 10-24)

which is the same as

(1 x 10+24) div 20.0892654

or (1 x 10+22) div 0.200892654

4.9778 x 10+24

I have to say that these seems remarkably complex for an 11+ question and I think they would certainly need to have a calculator.

This sounds like the sort of question that they only put as a scholarship question at the end of a Independent Schools maths paper.

What area do you live and where did you get the question from?

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 Post subject: maths helpPosted: Tue Oct 17, 2006 8:09 am
Hi thanks for your response we are moving to Kent and my daughters tutor set the question for practice for 11 plus

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 Post subject: Posted: Tue Oct 17, 2006 3:02 pm

Joined: Fri Sep 15, 2006 8:51 am
Posts: 8113
blimey looks like the sort of thing I was doing at O level 30 years ago....

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 Post subject: crazy tutorPosted: Thu Oct 19, 2006 2:26 pm
that sort of question would never appear in the Kent 11+. Buy the NFER practice papers to see the types that are set ......... and maybe get a different tutor!

Or are you aiming for an independent school in Kent which sets this type of question?

Good luck!

p.s. is your tutor a thwarted physicist?

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 Post subject: Posted: Mon Oct 23, 2006 10:31 pm
Kate3, I have to agree with Unsure. Those sort of questions are outside the scope of 11 plus; perhaps its off the NASA entrance paper!? KenR is obviously a candidate

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