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# Gunther, the pizza delivery boy, went out from the store carrying pizz

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Joined: 04 Jan 2015
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Gunther, the pizza delivery boy, went out from the store carrying pizz [#permalink]

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Updated on: 10 May 2018, 03:04
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Application of Average Speed in Distance problems - Exercise Question #2

Gunther, the pizza delivery boy, went out from the store carrying pizzas to deliver for the residents in 3 housing societies named Hufflepuff, Ravenclaw, and Slytherin. He started at 6:30 pm from the shop at a speed of 15 mph. After 15 minutes he reached Hufflepuff Society, and it took 15 minutes to deliver all pizzas there. Then at the same speed he moved for another 15 minutes to reach Ravenclaw, and in 15 minutes delivered all pizza. Finally, he drove towards Slytherin at double of his original speed, and after reaching there in 15 minutes time, he realised that the order has been cancelled. What is Gunther’s average speed in this whole journey (time includes delivery time)?

A. 8 mph
B. 10 mph
C. 12 mph
D. 15 mph
E. 30 mph

To solve question 3: Question 3

To read the article: Application of Average Speed in Distance problems
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Originally posted by EgmatQuantExpert on 09 May 2018, 08:33.
Last edited by EgmatQuantExpert on 10 May 2018, 03:04, edited 1 time in total.
e-GMAT Representative
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Gunther, the pizza delivery boy, went out from the store carrying pizz [#permalink]

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Updated on: 14 May 2018, 00:27

Solution

Given:
• Gunther delivered pizzas in three different societies – Hufflepuff, Ravenclaw, and Slytherin
• He started his journey at 6:30 pm from the shop at a speed of 15 mph
• In 15 minutes, he reached Hufflepuff society and took 15 minutes to deliver all pizzas in that society
• He again travelled for another 15 minutes to reach Ravenclaw society at the same speed of 15 minutes
• At Ravenclaw society, he took 15 minutes to deliver all pizzas in that society
• He again travelled for another 15 minutes to reach Slytherin society, at double of original speed, i.e. 30 mph
• After reaching Slytherin society he found out that the order was cancelled in that society

To find:
• Gunther’s average speed in this whole journey (time includes delivery time)

Approach and Working:
All the information can be shown in the following table:

• As the journey is divided into three separate parts, let us calculate the journey distance first.
o From the shop to Hufflepuff society, Gunther travelled for 15 minutes at 15 mph
 Therefore, the distance covered = $$\frac{15}{60}$$ * 15 miles = $$\frac{15}{4}$$ miles
o From Hufflepuff society to Ravenclaw society, Gunther travelled for 15 minutes at 15 mph
 Therefore, the distance covered = $$\frac{15}{60}$$ * 15 miles = $$\frac{15}{4}$$ miles
o From Ravenclaw society to Slytherin society, Gunther travelled for 15 minutes at 30 mph
 Therefore, the distance covered = $$\frac{30}{60}$$ * 15 miles = $$\frac{15}{2}$$ miles
o Hence, the total distance covered = ($$\frac{15}{4} + \frac{15}{4} + \frac{15}{2}$$) miles = $$\frac{60}{4}$$ miles = 15 miles

• Now, let’s calculate the total journey time
o From the shop to the delivery at Hufflepuff society, Gunther travelled for 15 minutes and delivered pizzas for 15 minutes
 Therefore, the total time taken = (15 + 15) = 30 minutes
o From Hufflepuff society to the delivery at Ravenclaw society, Gunther travelled for 15 minutes and delivered pizzas for 15 minutes
 Therefore, the total time taken = (15 + 15) = 30 minutes
o From Ravenclaw society to Slytherin society, Gunther travelled for 15 minutes only
 Therefore, the total time taken = 15 minutes
o Hence, the total time taken in the whole journey = (30 + 30 + 15) minutes = 75 minutes

• As we already know the total distance travelled and the total journey time, we can say the average speed = total distance travelled/total time taken = $$\frac{15}{75}$$ miles per minutes = $$\frac{1}{5}$$ miles per minute = $$\frac{1}{5}$$ * 60 mph = 12 mph

Hence, the correct answer is option C.

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Originally posted by EgmatQuantExpert on 09 May 2018, 08:34.
Last edited by EgmatQuantExpert on 14 May 2018, 00:27, edited 1 time in total.
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Re: Gunther, the pizza delivery boy, went out from the store carrying pizz [#permalink]

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13 May 2018, 08:38
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KUDOS
Average Speed = Total Distance / total time
Now Total Distance = 15 (1/4+1/4)+30*1/4 =15miles
Time = 15+15+15+15+15 = 75 min = 75/60 =5/4 hr
Average Speed = 15/(5/4)= 12mph
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Re: Gunther, the pizza delivery boy, went out from the store carrying pizz   [#permalink] 13 May 2018, 08:38
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