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#101 2006-10-16 15:51:29

ganesh
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Re: 10 second questions

Excellent performance, Devante` and mathsyperson,
You are correct.
I wonder how you manage to do it in under 10 seconds.

54. What is the volume of a room of length 12 feet, breadth 12 feet and height 12 feet?

55. How many square meters is a hectare?


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#102 2006-10-16 18:10:22

Devantè
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Re: 10 second questions

54. 1728
55. There are 10,000 square meters in a hectare.

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#103 2006-10-16 19:41:12

ganesh
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Re: 10 second questions

YOU ARE ABSOLUTELY RIGHT, DEVANTE`.


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#104 2006-10-16 19:45:49

Toast
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Registered: 2006-10-08
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Re: 10 second questions

Are we allowed to use calculators?

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#105 2006-10-16 19:48:09

ganesh
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Re: 10 second questions

NO................................................
All the calculations should be done by the brain big_smile


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#106 2006-10-16 19:51:09

ganesh
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Re: 10 second questions

56. What is sin²360°  + cos²360°  ?

57. What are the prime factors of 1001?

58. Is 4096 a perfect square?

59. How much percentage is 4 greater than 3?

60. What is the value of 2^10?


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#107 2006-10-17 00:42:22

mathsyperson
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Re: 10 second questions

56. 1, just like any other sin² + cos² thing. In this case it's even easier though, because it's just 0 + 1.

57. 11 and 91. You can recognise that it's a multiple of 11 with the nifty trick I used before, and then divide by 11 to get the 91.

58. 4096 = 2^12 = (2^6)² = 64². So yes. I know my powers of 2 too well. roll

59. (4-3)/3 x 100% = 33.333...%

60. 2^10 = 1024.


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#108 2006-10-17 03:54:32

Devantè
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Re: 10 second questions

56. 1
57. 11 and 91 - That's what I got, at least
58. 4096. I have studied the doubling of numbers (especially 2) for a long time. Didn't have to think much
59. 33.333....(recurring)
60. 1024 (I know my doubles and exponents of 2 tongue )

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#109 2006-10-17 15:57:47

ganesh
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Re: 10 second questions

Devante`and mathsy,
Your answers are all correct.
I wonder whether you use a calculator.
The prime factors of 1001 are 7, 11, 13.
Very well done, Devante`!


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#110 2006-10-17 16:14:06

ganesh
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Re: 10 second questions

61. If 12 numbers is a dozen, what is 12 dozens?

62. What is the significance of 9.8 m/s² ?


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#111 2006-10-17 18:20:42

Devantè
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Re: 10 second questions

ganesh wrote:

Devante`and mathsy,
Your answers are all correct.
I wonder whether you use a calculator.
The prime factors of 1001 are 7, 11, 13.
Very well done, Devante`!

No, no calculators. I solve them in my head. Sometimes I say the working out to myself. tongue

61. 12^2 = 144, simple tables
62. To convert between units of force and mass, we need to know the strength of gravity. Usually this is the so-called standard gravity (approximately 9.8 m/s² or 32 ft/s²).

To extend on question 62:

Plugging this value into Newton's second law, F = ma (force = mass × acceleration), we see that a one-kilogram mass experiences a gravitational force of 1 kg × 9.8 m/s² = 9.8 newtons. In general, to convert mass in kilograms to force in newtons (at the earth's surface), multiply by 9.8. Conversely, to convert newtons to kilograms divide by 9.8. (32 is the conversion factor for US Customary Units).

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#112 2006-10-17 21:43:49

mathsyperson
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Re: 10 second questions

Oh, boo. I can't believe I forgot to split 91. That's annoying. Ah well.

And I agree with both of Devanté's most recent answers. I know my squares almost as much as I know by powers of 2, and I had to use the 9.8 one very frequently for about 2 years of a mechanics course, so I'm not about to forget it.


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#113 2006-10-18 02:46:21

Devantè
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Re: 10 second questions

13?! Ugh, I didn't even think of that. >_>

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#114 2006-10-18 15:56:25

ganesh
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Re: 10 second questions

61. 12 dozens is a gross.

62. 9.8 is the acceleration due to gravity. You are right, Devante` and mathsyperson, this is often used in mechanics.


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#115 2006-10-18 18:28:16

Devantè
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Re: 10 second questions

For #61, I wasn't sure which you wanted, twelve dozen as a number of gross. tongue

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#116 2006-10-18 20:26:48

ganesh
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Re: 10 second questions

63. What are the prime factor(s) of 256?

64. What is the value of 7 x 7 x 7?


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#117 2006-10-18 23:28:57

mathsyperson
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Re: 10 second questions

63. 256 = 2[sup]8[/sup]. Yay for powers of 2!

64. 343. Yay for cubes!


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It wanted to be normal.

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#118 2006-10-19 03:02:35

Devantè
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Re: 10 second questions

63. 2^8
64. 343; knew off by heart

(Powers of 2! or 2? tongue )

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#119 2006-10-19 03:17:25

mathsyperson
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Re: 10 second questions

I had a feeling that someone would go pedantic on me. But 2! = 2 so it doesn't matter so ha.


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It wanted to be normal.

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#120 2006-10-19 18:21:21

Devantè
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Re: 10 second questions

Yes, I love to comment on typos. big_smile

At least there isn't a value for '2?'. Or, as far as I know.

Also, 2! = two!?

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#121 2006-10-21 15:25:11

John E. Franklin
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Registered: 2005-08-29
Posts: 3,564

Re: 10 second questions

Is the special number 26 from Avogadro's number?


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#122 2006-10-23 16:10:31

ganesh
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Re: 10 second questions

No, John.
26 is the only number jammed between a perfect square (25) and a perfect cube (27). I had read this somewhere but I don't know how that can be proved.
Avogadro Number is roughly 6.023x10^23.


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#123 2006-10-24 16:19:13

ganesh
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Re: 10 second questions

65. What is 2^20?

66. How many prime factors are there in 729?


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#124 2006-10-24 19:04:19

Devantè
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Posts: 6,400

Re: 10 second questions

65. 1048576 (a long time ago, we had a competition to see who could get the farthest in doubling from 1 in 2 minutes, plus knowing doubles)
66. 729 = 3x3x3x3x3x3

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#125 2006-10-30 01:57:45

ganesh
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Re: 10 second questions

Devante`,
Thats absolutely remarkable performance.

67. How many prime factors does 7776 have?

68. Whats the value of 7!?


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