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A certain bridge is 4,024 feet long. Approximately how many minutes... [#permalink]
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26 May 2016, 21:34
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A certain bridge is 4,024 feet long. Approximately how many minutes does it take to cross this bridge at a constant speed of 20 miles per hour? (1 mile = 5,280 feet) (A) 1 (B) 2 (C) 4 (D) 6 (E) 7
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Re: A certain bridge is 4,024 feet long. Approximately how many minutes... [#permalink]
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26 May 2016, 21:59
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In this question unit of measurements have to be taken care of.
Distance: 4024 feet. This is (4024/5280) miles = 0.76 miles
Speed: 20 miles per hour
Time: (Distance / Speed) (0.76/20) {This will come in Hours}. Multiply by 60 to get answer in minutes. It is 2.28 minutes.
Answer to be 2 minutes.



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Re: A certain bridge is 4,024 feet long. Approximately how many minutes... [#permalink]
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14 Jun 2016, 12:34
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nalinnair wrote: A certain bridge is 4,024 feet long. Approximately how many minutes does it take to cross this bridge at a constant speed of 20 miles per hour? (1 mile = 5,280 feet)
(A) 1 (B) 2 (C) 4 (D) 6 (E) 7 First, convert the speed to feet per minute. 20 miles per hour = ( 20 * 5280 ) feet per 60 minutes. Time = \(\frac{Distance}{Speed}\) = \(\frac{4024}{(20 * 5280 ) / 60}\) = \(\frac{4024 *60}{20 * 5280}\) = \(\frac{4024 * 3}{5280}\) = \(\frac{4024}{5280}\)*3 \(\frac{4024}{5280}\) < 1. Therefore, Time < 3. We can eliminate (A) because \(\frac{4024}{5280}\) is not equal to \(\frac{1}{3}\). The only answer choice remaining is (B). Therefore, (B) is the answer.



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A certain bridge is 4,024 feet long. Approximately how many minutes... [#permalink]
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14 Jun 2016, 12:57
~3/4 miles/(1/3) mpm=~2 minutes



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Re: A certain bridge is 4,024 feet long. Approximately how many minutes... [#permalink]
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19 Mar 2017, 12:01
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Here's another method that allowed me to solve the question in approximately 30 seconds:
20 miles per hour translates to traveling 1 mile every 3 minutes. Since the bridge is longer than 1/2 mile but shorter than 1 mile, the answer must be between 1.5 and 3 minutes. The only answer choice that fits this range is 2 minutes.



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Re: A certain bridge is 4,024 feet long. Approximately how many minutes... [#permalink]
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19 Mar 2017, 12:32
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Does anyone have a tip for a quick way to solve the division of 4024/5280? This is where I spend the majority of my time on the problem and am wondering if I can do something faster. I do a lot of trial and error.



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Re: A certain bridge is 4,024 feet long. Approximately how many minutes... [#permalink]
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20 Mar 2017, 01:56
nalinnair wrote: A certain bridge is 4,024 feet long. Approximately how many minutes does it take to cross this bridge at a constant speed of 20 miles per hour? (1 mile = 5,280 feet)
(A) 1 (B) 2 (C) 4 (D) 6 (E) 7 distance = 4024 ft = 4024/5280 miles time taken = 4024/5280*20 hours= 0.76 hours = 2.28 minutes close to 2 minutes option B



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Re: A certain bridge is 4,024 feet long. Approximately how many minutes... [#permalink]
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20 Mar 2017, 21:25
Hi amandakay, The GMAT would never expect you to calculate the exact value of 4024/5280, so if you're ever thinking about doing something so "calculation heavy", then there's almost certainly a faster or easier way to get to the correct answer. In this prompt, you should notice the word "approximately"  that means that you DON'T have to calculate that fraction, but you do have to estimate the value. If we 'round down', then 4024 ft./5280 ft. is a little less than 4/5 of a mile. Knowing THAT, and that 20 mph is 1 mile every 3 minutes, can you correctly answer the question? GMAT assassins aren't born, they're made, Rich
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A certain bridge is 4,024 feet long. Approximately how many minutes... [#permalink]
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23 Jun 2017, 17:14
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Approximation! D=4000 R=20mph Convert it to miles per minutes = \(\frac{20}{60}\) R = \(\frac{1}{3}\) 1 mile = approx 5000 feet \(T=\frac{D}{R}\) \(=\frac{(4000*3)}{5000}\) \(=\frac{12000}{5000}\) \(=\frac{12}{5}\) = 2.4 Since the denominator is slightly more than 5000, the value will be less than 2.4. i.e B
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Re: A certain bridge is 4,024 feet long. Approximately how many minutes... [#permalink]
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07 Apr 2018, 03:52
nalinnair wrote: A certain bridge is 4,024 feet long. Approximately how many minutes does it take to cross this bridge at a constant speed of 20 miles per hour? (1 mile = 5,280 feet)
(A) 1 (B) 2 (C) 4 (D) 6 (E) 7 hello friends here is a quick way to solve it if 20 miles = 60 min> then 1 mile = 3 min if length of bridge (4,024 feet) is shorter than 1 mile (5,280 feet) then only option is B




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