Surds and the use of PI calculation help

[Markfringe]

3√(651/(4pi)) simplify to four decimal placings

I would have thought it would be done as Brackets first

3√(651/(4*3.1415) =
3√(651/12.566) =
3√(51.8065) =
3*√51.8065=
3*√51.8065 =
3*7.1977 = 21.5930

Can some please show me where i am wrong as the answer book give it as = 3.728 (to 4 significant figures)

 

[Markfringe]

idiots do some times learn

Dano2 is a legend :grin::lol:
See his answer below............ if we just read the question correctly !!

Which actually read "CUBE ROOT of (651/(4pi))" not as we mistakenly saw it as "3 times the sq-root"

I see, the problem is that it is not 3 TIMES anything, it is the CUBE ROOT of (651/(4pi)), which is 3.7278

http://www.wolframalpha.com/input/?i=cube+root+of+[651/(4pi)]

I would have thought it would be done as Brackets first

cube root(651/(4*3.1415) =
cube root(651/12.566) =
cube root(51.8065) = 3.7278

idiots do some times learn... thanks DANO2

 

[lookagain]

3√(651/(4pi)) simplify to > > > four decimal placings < < < \(\displaystyle \ \ \ \ \) This phrase appears to be inconsistent with the phrase in the last sentence of this quote box.

I would have thought it would be done as Brackets first

3√(651/(4*3.1415) =
3√(651/12.566) =
3√(51.8065) =
3*√51.8065=
3*√51.8065 =
3*7.1977 = 21.5930

Can some please show me where i am wrong as the answer book give it as = > > > 3.728 (to 4 significant figures) < < <

If the problem proposer had intended the cube root of something, then they had better use some correct symbol for it!

For instance, if I type "3√2," that is three multiplied by the square root of two, not the cube root of two.

I would have thought it would be done as Brackets first

cube root(651/(4*3.1415) = \(\displaystyle \ \ \ \ \ \) 1) Don't truncate digits. Anyway, 3.1416 is closer to pi than is 3.1415.



cube root(651/12.566) =\(\displaystyle \ \ \ \ \ \ \) In general, carrying more exact decimal digits is better (up to a point). And round only down to the nearest four decimal places at the end of the solution.[/b]




cube root(51.8065) = 3.7278 \(\displaystyle \ \ \ \ \ \ \) <-------- You lucked out that this is correct to the nearest four decimal places.

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