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PostPosted: Thu Apr 21, 2016 3:26 pm 
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Joined: Fri Mar 02, 2012 9:33 am
Posts: 147
5³ - 10² = ?⁵

steps please


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PostPosted: Thu Apr 21, 2016 3:30 pm 
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well I think I would turn it into normal numbers

5^3 = 125
10^2 = 100

so 125-100=25

or 5^2


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PostPosted: Thu Apr 21, 2016 3:30 pm 
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Joined: Tue Oct 27, 2009 8:19 pm
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5x5x5 - 10x10

125 - 100

= 25

Ds2 tells me this is BIDMAS

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Knowledge is knowing that a tomato is a fruit, wisdom is not putting it in a fruit salad !


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PostPosted: Thu Apr 21, 2016 3:36 pm 
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Thanks, I did know how to solve the first part, looking for ?

but the answer has to be to the power of 5

I am looking for ? in this sum ?⁵

:roll:


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PostPosted: Thu Apr 21, 2016 3:37 pm 
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Has to be a typo if an 11+ question.


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PostPosted: Thu Apr 21, 2016 3:51 pm 
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I agree that its probably a typo and should read ?^2 rather than ?^5.

(If it really is ?^5, then ? = 25^(1/5) = 1.904 )


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PostPosted: Thu Apr 21, 2016 3:54 pm 
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Thanks proud Dad.

This is non-calculator, can you tell me the steps you used to get to 1.904


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PostPosted: Thu Apr 21, 2016 4:00 pm 
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topsyturvy wrote:
Thanks proud Dad.

This is non-calculator, can you tell me the steps you used to get to 1.904


Unless you use log tables you can't do this without a calculator I don't think. Not easily anyway. Unless you use trial and improvement, that would take for ever.

There is a way of finding out square roots without a calculator (I learnt, then forgot it many many moons ago) but I wouldn't expect any child these days to have a clue, let alone finding a 5th root.


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PostPosted: Thu Apr 21, 2016 4:10 pm 
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topsyturvy wrote:
Thanks proud Dad.

This is non-calculator, can you tell me the steps you used to get to 1.904


I didn't strictly use a calculator (but I did use the calc app on my mobile to work out 25^0.2 :mrgreen: )

You can't really do it without a calculator tbh. Only way I can think of to do a rough estimate in my head is that 2^5 = 32 so the answer would be a bit less than 2.

As I and others said I think the question has a typo.


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PostPosted: Thu Apr 21, 2016 4:19 pm 
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Thank you, much appreciated for all replies and feedback!


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