Q1: In which of the following situations, does the list of numbers involved make an arithmetic progression, and why?
(iii) The cost of digging a well after every metre of digging, when it costs for the first metre and rises by for each subsequent metre.
It is given that the cost of digging a 1st metre = Rs 150
and rises by for each subsequent metre
Therefore,
cost of digging the first 2 metres = cost of digging the first metre + cost of digging additional metre
cost of digging the first 2 metres = 150 + 50
= Rs 200
Similarly,
The cost of digging the first 3 metres = cost of digging the first 2 metres + the cost of digging an additional metre
Cost of digging the first 3 metres = 200 + 50
= Rs 250
We can clearly see that 150, 200, 250,... is in AP with each subsequent term is obtained by adding a fixed number (50) to the previous term.
Therefore, it is an AP with first term (a) = 150 and common difference (d) = 50