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3 years ago

23) It takes a bus 6 hours to take a trip. The train takes only 4 hours to make the same trip. The train travels

Mathematics

1 answer:

sammy [17]3 years ago

8 0

Answer:

x = 50 mph speed of the bus

y = 75 mph speed of the train

Step-by-step explanation:

Lt´s call "x" speed of bus and "y" speed of train.

According to the problem statement

6*x = 4*y (1)

y = x + 25 (2)

We solve for x and y the two equation system

y = ( 6/4)*x

( 6/4)*x = x + 25

6*x = 4*x + 100

2*x = 100

x = 50 mph

And

y = (6/4)*x

y = 300/4

y = 75 mh

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levacccp [35]

Answer:

Step-by-step explanation:

From the given information:

There are 30 collections of gems, of which 8 are worthless;

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$Pr (X = 0) = \dfrac{\dfrac{8!}{2!(8-2)!}}{435} \\ \\ Pr (X = 0) = \dfrac{\dfrac{8!}{2!(6)!}}{435} \\ \\ Pr (X = 0) = \dfrac{\dfrac{8*7*6!}{2!(6)!}}{435} \\ \\ Pr (X = 0) = \dfrac{\dfrac{8*7}{2*1}}{435} \\ \\ Pr (X = 0) = 0.0644$

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$P(X =1200) =0.4046$

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$Pr (X = 2400) = \dfrac{\dfrac{22!}{2!(22-2)!}}{435} \\ \\ Pr (X = 2400) = \dfrac{\dfrac{22!}{2!(20)!}}{435} \\ \\ Pr (X = 2400) = \dfrac{\dfrac{22*21*20!}{2!(20)!}}{435} \\ \\ Pr (X =2400) = \dfrac{\dfrac{22*21}{2*1}}{435} \\ \\ Pr (X = 2400) = 0.5310$

To find E(X):

E(X) = (0 × 0.0644) + (1200 × 0.4046) + (2400 × 0.5310)

E(X) = 0 + 485.52 + 1274.4

E(X) = 1759.92

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