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Arithmetic Progressions

Question
CBSEENMA10007384

In which of the following situations, does the list of numbers involved make an arithmetic progression, and why?

The taxi fare after each km when the fare is Rs. 15 for the first km and Rs. 8 for each additional km.

Solution

Taxi fare for 1 km = Rs. 15 = aTaxi fare for 2 kms
= Rs. 15 + Rs. 8 = Rs. 23 = aTaxi fare for 3 kms
= 23 + Rs. 8 = Rs. 31 = aTaxi fare for 4 kms
= Rs. 31 + Rs. 8 = Rs. 39 = a4
and so on.
a– a1 = Rs. 23 – Rs. 15 = Rs. 8
a3 – a2 = Rs. 31 – Rs. 23 = Rs. 8
a4 – a3 = Rs. 39 – Rs. 31 = Rs. 8
i.e., ak + 1 – ak is the same every time.