Math Destroyer Test 11 #25 and #37

[Wererew]

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I can't wrap my head around these two questions too well so I wanted to reach out on here for help

#25

If train A is traveling faster than train B, why does train A need to catch up to train B? Also, if we are at the same starting point, when is there a time where the tip of train A is going to be behind train B?

I might not be thinking correctly so any input is appreciated! I tried drawing two trains but didn't work haha


#37

Anyone willing to explain step by step? I figured we needed to do 2 probabilities incorporated into one

Thank you!

 

[DAT Destroyer]

I can't wrap my head around these two questions too well so I wanted to reach out on here for help

#25

If train A is traveling faster than train B, why does train A need to catch up to train B? Also, if we are at the same starting point, when is there a time where the tip of train A is going to be behind train B?

I might not be thinking correctly so any input is appreciated! I tried drawing two trains but didn't work haha


#37

Anyone willing to explain step by step? I figured we needed to do 2 probabilities incorporated into one

Thank you!

Question #25
For train A to completely pass train B, it has to travel it's own length plus the length of train B which is 410+390 = 800 ft.
Since both trains are moving in the same direction, the speed of A relative to B is : 90 - 40 = 50 mph
Convert 50 mph to fps ( the conversion factor is given in the problem). 50*88/60
Then to find time use : t = d/v

Question 27

Another way of doing this problem is as follow:
Since we're choosing 3 paintings with at least one Kandinsky we have the following possibilities: KCC, KKC and KKK
For KCC we have 6C1*4C2
That is how many ways we can pick 1 kandinsky out of 6 times how many times we can pick 2 Chagals out of 4.
For KKC we have : 6C2*4C1.
For KKK we have: 6C3.
Add all to get 116

 

[Wererew]

Question #25
For train A to completely pass train B, it has to travel it's own length plus the length of train B which is 410+390 = 800 ft.
Since both trains are moving in the same direction, the speed of A relative to B is : 90 - 40 = 50 mph
Convert 50 mph to fps ( the conversion factor is given in the problem). 50*88/60
Then to find time use : t = d/v

Question 27

Another way of doing this problem is as follow:
Since we're choosing 3 paintings with at least one Kandinsky we have the following possibilities: KCC, KKC and KKK
For KCC we have 6C1*4C2
That is how many ways we can pick 1 kandinsky out of 6 times how many times we can pick 2 Chagals out of 4.
For KKC we have : 6C2*4C1.
For KKK we have: 6C3.
Add all to get 116

Thank you so much!