Large percentage problem: check my work please?

[Holocene]

The universe is thought to be 13.7 Billions years old. If you lived to be 100, what percentage of the total age of the universe would coincide with your lifetime?

I get .0000007% or seven 10-Millionths of one percent.

Is this correct?

 

[Gib Z]

\frac{100}{1.37\cdot10^{10}} \cdot 100 = \frac{10^4}{1.37\cdot 10^{10}} = \frac{1}{1.37\cdot10^6} = 7.2992700729927\cdot 10^{-8}

So you got close, but there's a bit more accurate.

 

[Holocene]

I'm a bit confused here.

1 / 1.37 x 10^6 = 1 / 1,370,000 = 0.00000073 = 7.3 x 10^-7

7.3 x 10^-7 does not equal 7.2992700729927 x 10^-8

What am I doing wrong?

 

[Gib Z]

Well first when you have 13.7 BILLION years the exponent of the 10 is 9, not 6. 6 Is for million. So its 13.7 x 10^9. 13.7 is 1.37 x 10, so it becomes 1.37x10^10

I don't see what the problem should be, you have the right answer in the beginning! I just gave it a bit more accurately.

 

[Moo Of Doom]

I don't see what the problem should be, you have the right answer in the beginning! I just gave it a bit more accurately.

You did the right steps, just made a typo at the end.

\frac{1}{1.37\cdot10^6} = 7.2992700729927\cdot 10^{-7}
not
\frac{1}{1.37\cdot10^6} = 7.2992700729927\cdot 10^{-8}

 

[Gib Z]

You did the right steps, just made a typo at the end.

\frac{1}{1.37\cdot10^6} = 7.2992700729927\cdot 10^{-7}
not
\frac{1}{1.37\cdot10^6} = 7.2992700729927\cdot 10^{-8}

Damn it! Yes Moo's right...

 

[uart]

I find this thread really ironic. Holocene got the most correct answer, though apparently by accident of inexperience with his calculator and scientific notation etc.

Gib Z and Moo, you should know it's bad form to give an answers to 15+ significant digits when the data on which the calculations are based is dubious at even two or three significant digits.

 

[Gib Z]

Gib Z and Moo, you should know it's bad form to give an answers to 15+ significant digits when the data on which the calculations are based is dubious at even two or three significant digits.

14 hehe..Lets settle with 7.3 \cdot 10^{-7} :)