The product of the five smallest two-digit prime numbers

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The product of the five smallest two-digit prime numbers [#permalink]

09 Aug 2012, 09:57

00:00

Question Stats:

62% (01:50) correct

37% (01:00) wrong

based on 2 sessions

The product of the five smallest two-digit prime numbers is closest to which of the following powers of 10?

(A) 10^9
(B) 10^8
(C) 10^7
(D) 10^6
(E) 10^5

A faster way to solve it?

Source: http://www.gmathacks.com

[Reveal] Spoiler: OA

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Re: The product of the five smallest two-digit prime numbers [#permalink]

09 Aug 2012, 10:29

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metallicafan wrote:

The product of the five smallest two-digit prime numbers is closest to which of the following powers of 10?
(A) 10^9
(B) 10^8
(C) 10^7
(D) 10^6
(E) 10^5

A faster way to solve it?

Source: http://www.gmathacks.com

The product is 11*13*17*19*23

Try some approximation:
10*15*15*20*20 = 4,000*225=900,000, this would be somewhat smaller than the real product.
10*15*15*20*25 = 2250*500=1,250,000, this for sure is larger.
My bet is 10^6.
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Re: The product of the five smallest two-digit prime numbers [#permalink]

09 Aug 2012, 14:54

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The product of the five smallest two-digit prime numbers is closest to which of the following powers of 10?
(A) 10^9
(B) 10^8
(C) 10^7
(D) 10^6
(E) 10^5

One can also use the following approximation:

11*13*17*18*23\approx{10*10*20*20*25}=100*10,000=10^6

Answer: D.

Similar question to practice:
the-product-of-the-fir-st-eight-positive-even-integers-is-128135.html
the-product-of-all-the-prime-numbers-less-than-20-is-closest-135192.html (from OG)

Hope it helps.
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Re: The product of the five smallest two-digit prime numbers [#permalink] 09 Aug 2012, 14:54

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The product of the five smallest two-digit prime numbers

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The product of the five smallest two-digit prime numbers

The product of the five smallest two-digit prime numbers

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