BahnCard 25 / 50 / 100 Question

Math problem Real interview question
Recent activity on Jul 26, 2017
1 Answer
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Anonymous A asked on Jul 25, 2017

Hi guys,

the following interview question came up recently:

BahnCard 25 costs 50 €
BahnCard 50 costs 200 €
BahnCard 100 costs 3000 €

(for international prepers: BahnCard is a loyalty card of the german railroad company that costs the stated amount and provides a discount which is given in the name)

1. How many kilometers do you have to travel to break even with each BahnCard (easy and solved)

2. From how many kilometers on exactly is BahnCard 100 the better choice?

To make it easy the interviewer assumed that 1km costs 1 €.

Thank you very much :)

(edited)

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Anonymous B replied on Jul 26, 2017

Answer should be 5600km.

1. Find total kms where: Avg. BC25 = BC100 (50 + x*0.75)/x = 3000/x

2. Find total kms where: Avg. BC50 = BC100 (200 + x*0.50)/x = 3000/x

The larger answer is the correct one.

Hint:

At ≈4000km BC100 would have a lower Avg. (cost / km) than BC25

At ≈5600km BC100 would have a lower Avg. (cost / km) than BC50

Anything beyond 5600km, BC100 would cost nothing, but BC50 would still carry an additional charge of €0.50/km.

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Joe on Jul 26, 2017

thanks!

(edited)