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29 Apr 2025, 08:37
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B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
76% (00:51) correct
24%
(01:04)
wrong
based on 41
sessions
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Bob traveled from his home to his office and then returned home along the same route. What was Bob’s average speed for the entire trip?
(1) The distance between Bob’s home and his office is 45 kilometers.
(2) On the way to the office, Bob’s speed averaged 60 kilometers per hour, and on the way back, his speed averaged 90 kilometers per hour.
Gentle note to all experts and tutors: Please refrain from replying to this question until the Official Answer (OA) is revealed. Let students attempt to solve it first. You are all welcome to contribute posts after the OA is posted. Thank you all for your cooperation!
(1) The distance between Bob’s home and his office is 45 kilometers.
(2) On the way to the office, Bob’s speed averaged 60 kilometers per hour, and on the way back, his speed averaged 90 kilometers per hour.
Gentle note to all experts and tutors: Please refrain from replying to this question until the Official Answer (OA) is revealed. Let students attempt to solve it first. You are all welcome to contribute posts after the OA is posted. Thank you all for your cooperation!
10 May 2025, 06:30
Kudos
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Official Solution:
Bob traveled from his home to his office and then returned home along the same route. What was Bob’s average speed for the entire trip?
The average speed can be found by \(\frac{total\ distance}{total\ time}\).
(1) The distance between Bob’s home and his office is 45 kilometers.
Knowing only the distance is not enough to get the average speed. Not sufficient.
(2) On the way to the office, Bob’s speed averaged 60 kilometers per hour, and on the way back, his speed averaged 90 kilometers per hour.
Assuming that the distance to and from is \(d\) kilometrs, the above implies that the trip to the office would take Bob \(\frac{d}{60}\) hours, and the trip from the office would take hime \(\frac{d}{90}\) hours. Therefore, the average speed would be \(\frac{2d}{\frac{d}{60} + \frac{d}{90}}\). We can reduce by \(d\) and calalte the exact value. Sufficient.
Assuming that the distance one way is \(d\) kilometers, the trip to the office would take Bob \(\frac{d}{60}\) hours, and the trip back would take him \(\frac{d}{90}\) hours. Therefore, the average speed would be \(\frac{2d}{\frac{d}{60} + \frac{d}{90}}\). We can reduce by \(d\) and calculate the exact value. Sufficient.
Answer: B
Bob traveled from his home to his office and then returned home along the same route. What was Bob’s average speed for the entire trip?
The average speed can be found by \(\frac{total\ distance}{total\ time}\).
(1) The distance between Bob’s home and his office is 45 kilometers.
Knowing only the distance is not enough to get the average speed. Not sufficient.
(2) On the way to the office, Bob’s speed averaged 60 kilometers per hour, and on the way back, his speed averaged 90 kilometers per hour.
Assuming that the distance to and from is \(d\) kilometrs, the above implies that the trip to the office would take Bob \(\frac{d}{60}\) hours, and the trip from the office would take hime \(\frac{d}{90}\) hours. Therefore, the average speed would be \(\frac{2d}{\frac{d}{60} + \frac{d}{90}}\). We can reduce by \(d\) and calalte the exact value. Sufficient.
Assuming that the distance one way is \(d\) kilometers, the trip to the office would take Bob \(\frac{d}{60}\) hours, and the trip back would take him \(\frac{d}{90}\) hours. Therefore, the average speed would be \(\frac{2d}{\frac{d}{60} + \frac{d}{90}}\). We can reduce by \(d\) and calculate the exact value. Sufficient.
Answer: B
General Discussion
04 May 2025, 06:37
Kudos
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Bunuel
Let Bob travel a distance of D km from home to office.
Average Speed = Total distance travelled/ ( time taken = t1+t2)
Statement 1:
(1) The distance between Bob’s home and his office is 45 kilometers.
Given D = 45 km. Since we don’t know about the time or speed of the journeys. Insufficient.
Statement 2:
(2) On the way to the office, Bob’s speed averaged 60 kilometers per hour, and on the way back, his speed averaged 90 kilometers per hour.
Average speed = 2D / ([D/90]+ [D/60])
= 2*90*60/(90+60)
= 72 kmph
Hence, Sufficient .
Option B
