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# A biker increased his average speed by 10 miles per hour in each succe

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Math Expert
Joined: 02 Sep 2009
Posts: 50007
A biker increased his average speed by 10 miles per hour in each succe  [#permalink]

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26 Sep 2018, 05:04
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Difficulty:

15% (low)

Question Stats:

84% (01:23) correct 16% (02:05) wrong based on 31 sessions

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A biker increased his average speed by 10 miles per hour in each successive 10-minute interval after the first interval. If in the first 10-minute interval, his average speed was 30 miles per hour, how many miles did he travel in the fourth 10-minute interval?

(A) 4
(B) 5
(C) 8
(D) 10
(E) 15

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Joined: 19 Apr 2017
Posts: 37
A biker increased his average speed by 10 miles per hour in each succe  [#permalink]

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29 Sep 2018, 12:48
Question asks us to find distance. Since Time and speed is given so $$Distance = Speed x Time$$

Time is giving in min…. convert Time to hour to make it uniform so time becomes $$10/60 = 1/6 hour$$

Distance at First interval $$= Speed*time = 30*1/6$$
Distance at Second interval $$= Speed*time = 40*1/6$$
Distance at Third interval $$= Speed*time = 50*1/6$$

Distance at Fourth interval$$= Speed*time = 60*1/6=10$$ Ans D
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Joined: 22 May 2016
Posts: 2037
A biker increased his average speed by 10 miles per hour in each succe  [#permalink]

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29 Sep 2018, 21:25
Bunuel wrote:
A biker increased his average speed by 10 miles per hour in each successive 10-minute interval after the first interval. If in the first 10-minute interval, his average speed was 30 miles per hour, how many miles did he travel in the fourth 10-minute interval?

(A) 4
(B) 5
(C) 8
(D) 10
(E) 15

A biker increases his average speed by 10 mph for each successive interval.
Speed is 30 mph during the first interval

Speed during 4th interval?

1st-> 2nd-> 3rd--> 4th
30 --> 40 --> 50 -> 60 mph

1 hour = 60 minutes
A speed of $$\frac{60mi}{1hour}=\frac{60mi}{60min}$$

Miles traveled in 4th interval? (r*t) = D
t = 10 minutes (each interval is 10 minutes)

Miles traveled: $$(\frac{60mi}{60mins}* 10 mins)=\frac{60}{6}mi=10$$ miles

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A biker increased his average speed by 10 miles per hour in each succe &nbs [#permalink] 29 Sep 2018, 21:25
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