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# At a lab, bacteria P multiplies itself in every 18 days, while bacteri

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Math Expert
Joined: 02 Sep 2009
Posts: 58410
At a lab, bacteria P multiplies itself in every 18 days, while bacteri  [#permalink]

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24 Sep 2018, 01:31
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Difficulty:

95% (hard)

Question Stats:

22% (02:24) correct 78% (02:00) wrong based on 36 sessions

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At a lab, bacteria P multiplies itself in every 18 days, while bacteria Q multiplies itself in every 15 days. Approximately by what percent is the number of times bacteria Q multiplies itself is more than the number of times bacteria P multiplies itself in a 3-year period?

(A) 12%
(B) 16%
(C) 20%
(D) 22%
(E) 33%

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Re: At a lab, bacteria P multiplies itself in every 18 days, while bacteri  [#permalink]

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24 Sep 2018, 01:36
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Bunuel wrote:
At a lab, bacteria P multiplies itself in every 18 days, while bacteria Q multiplies itself in every 15 days. Approximately by what percent is the number of times bacteria Q multiplies itself is more than the number of times bacteria P multiplies itself in a 3-year period?

(A) 12%
(B) 16%
(C) 20%
(D) 22%
(E) 33%

Let, Total days = LCM (15 and 18) = 90

P multiplies 90/18 = 5 times in 90 days
Q multiplies 90/15 = 6 times in 90 days

i.e. in any given time (i.e. 3 years as well) the number of times bacteria Q multiplies itself is more than the number of times bacteria P multiplies itself = (6-5)*100/5 = 20%

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Re: At a lab, bacteria P multiplies itself in every 18 days, while bacteri  [#permalink]

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01 Oct 2018, 11:44
Bunuel wrote:
At a lab, bacteria P multiplies itself in every 18 days, while bacteria Q multiplies itself in every 15 days. Approximately by what percent is the number of times bacteria Q multiplies itself is more than the number of times bacteria P multiplies itself in a 3-year period?

(A) 12%
(B) 16%
(C) 20%
(D) 22%
(E) 33%

Bunuel

=73-61/61=20%
Where, Q multiplies 73 times and P 61 times.
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Joined: 12 Sep 2018
Posts: 27
At a lab, bacteria P multiplies itself in every 18 days, while bacteri  [#permalink]

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02 Oct 2018, 02:12
1
KS15 wrote:
Bunuel wrote:
At a lab, bacteria P multiplies itself in every 18 days, while bacteria Q multiplies itself in every 15 days. Approximately by what percent is the number of times bacteria Q multiplies itself is more than the number of times bacteria P multiplies itself in a 3-year period?

(A) 12%
(B) 16%
(C) 20%
(D) 22%
(E) 33%

Bunuel

=73-61/61=20%
Where, Q multiplies 73 times and P 61 times.

I too got C at first attempt.

But assuming a year composed by 365 days you get:
P multiplies $$\frac{(365*3)}{18}=60.833=60$$ times (P does not complete its 61st cycle)
Q multiplies $$\frac{(365*3)}{15}=73$$ times

$$\frac{73}{60}-1=0.2166$$ which is closer to 22%.
At a lab, bacteria P multiplies itself in every 18 days, while bacteri   [#permalink] 02 Oct 2018, 02:12
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