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The age of certain granite rocks found in northwestern Canada is

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felippemed
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The age of certain granite rocks found in northwestern Canada is [#permalink] New post   Updated on: 08 Nov 2023, 03:35
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The age of certain granite rocks found in northwestern Canada is approximately \(1.2×10^{17}\) seconds. Which of the following is closest to the age of these rocks, in years? (1 year is approximately \(3.2 × 10^7\) seconds.)

(A) \(3.8*10^9\)

(B) \(5.9*10^9\)

(C) \(2.0*10^{10}\)

(D) \(2.0*10^{11}\)

(E) \(3.8*10^{11}\)

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Originally posted by felippemed on 26 Sep 2016, 18:50.
Last edited by Bunuel on 08 Nov 2023, 03:35, edited 4 times in total.
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Re: The age of certain granite rocks found in northwestern Canada is [#permalink] New post   28 Sep 2016, 01:19
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Very simple one.

We are given \(1 year = 3.2 * 10^7 secs\)

or \(1 sec = 1 / (3.2 * 10^7)\)

Now, given seconds = \(1.2∗10^17\)

We can say \(1.2∗10^17\) = \((1.2∗10^17)/ (3.2 * 10^7)\) = \(3.8∗10^9\)

Hence , A
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Re: The age of certain granite rocks found in northwestern Canada is [#permalink] New post   16 Sep 2019, 08:39
felippemed wrote:
The age of certain granite rocks found in northwestern Canada is approximately \(1.2*10^{17}\) seconds. Which of the following is the closest to the age of theses rocks in years? (1 year is approximately \(3.2*10^7 seconds\).)

a) \(3.8*10^9\)
b) \(5.9*10^9\)
c) \(2.0*10^{10}\)
d) \(2.0*10^{11}\)
e) \(3.8*10^{11}\)


The age of certain granite rocks found in northwestern Canada is approximately \(1.2*10^{17}\) seconds. Which of the following is the closest to the age of theses rocks in years? (1 year is approximately \(3.2*10^7 seconds\).)

Age in years = 12*10^{16}/3.2*10^7 = 3.8 * 10^9 years

IMO A
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Re: The age of certain granite rocks found in northwestern Canada is [#permalink] New post   13 Aug 2020, 03:26
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felippemed wrote:
The age of certain granite rocks found in northwestern Canada is approximately \(1.2*10^{17}\) seconds. Which of the following is the closest to the age of theses rocks in years? (1 year is approximately \(3.2*10^7 seconds\).)

a) \(3.8*10^9\)
b) \(5.9*10^9\)
c) \(2.0*10^{10}\)
d) \(2.0*10^{11}\)
e) \(3.8*10^{11}\)



Time saving method:

Given: 1 year= 3.2*10^7
? years = 1.2*10^17

So 1.2*10^17/ 3.2*10^7= 12*10^16/3*10^7 =4*10^9

we approximated 3.2 to 3 for easier cal. since 3.2 > 3 our actual no of years has to be slightly less than 4*10^9

on checking ans choices. Option A has 3.8*10^9 which is closer to 4*10^9

Saves time to approximate .

Correct Ans - A

Hope that helps!
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Re: The age of certain granite rocks found in northwestern Canada is [#permalink] New post   19 Nov 2020, 11:45
felippemed wrote:
The age of certain granite rocks found in northwestern Canada is approximately \(1.2*10^{17}\) seconds. Which of the following is the closest to the age of theses rocks in years? (1 year is approximately \(3.2*10^7 seconds\).)

a) \(3.8*10^9\)
b) \(5.9*10^9\)
c) \(2.0*10^{10}\)
d) \(2.0*10^{11}\)
e) \(3.8*10^{11}\)


\(\frac{1.2*10^{17}}{3.2*10^7}\)
= \(\frac{3}{8}*10^{10}\)
= \(0.375 *10^{10}\)
= \(3.75 * 10^9\)

Closest answer is A.
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Re: The age of certain granite rocks found in northwestern Canada is [#permalink] New post   19 Aug 2023, 08:57
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Re: The age of certain granite rocks found in northwestern Canada is [#permalink]
19 Aug 2023, 08:57
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