by **Sahara**

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I live, laugh, love...,

read, write, teach...,

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its a very good point puddlepuff... its part of my course but my head hurts today... :(

16th Jan 2007, 13:18

Thanks Mat - but my brain has ceased to work!! how do i do it?!?! 10^12 is still the wrong answer...

16th Jan 2007, 13:24

The terms under the square root become 9 and 10 to the 5th power. Add the powers of 10 in the top and you have 10 to the 15th power times 9. The two nines cancel and some of the powers of ten cancel, leaving 10 to the 13th power divided by 4. So 2500000000000. I think.

16th Jan 2007, 13:32

I've done that four times now, twice the long way - each time I've got 9.4 x 10^12

it's been a *long* time since I've done any maths like this though.

16th Jan 2007, 13:37

The square root of 81 x 10^10 is 9 x 10^5. OK, this times 10^12 is 9 x 10^17.

If you divide 9 x 10^17 by 9.4 x 10^4, with a bit of rounding you get 9.574 x 10^12 :)

(the nines don't cancel, by the way. Sorry mtn_hermit :) )

Does that help?

[edit] oh, and an order of magnitude estimate would be 10^13 :)

16th Jan 2007, 13:39

Eureka Euphro ! Thanksyou SO much guys! It's the right answer... i originally came up with 10^12 too so I don't know what I did wrong..?

still another 21 questions to go.....

:(

want to help with all the others??? :p

16th Jan 2007, 13:46

If you find yourself stuck, we'll have a go, but I don't think that getting us to do them all for you (fun and all as that might be) would really be helping you :)

16th Jan 2007, 13:56