The cost of digging a well after every metre of digging, when it costs ₹ $150$ for the first metre and rises by ₹ $50$ for each subsequent metre, does the list of numbers involved make an arithmetic progression, and why?

(A) Cost of digging for the first metre $= ₹ 150$.
Cost of digging for the first $2$ metres $= 150 + 50 = ₹ 200$.
Cost of digging for the first $3$ metres $= 200 + 50 = ₹ 250$.
Cost of digging for the first $4$ metres $= 250 + 50 = ₹ 300$.
Clearly, the sequence $150, 200, 250, 300, \dots$ forms an Arithmetic Progression $(A.P.)$ because the difference between any two consecutive terms is constant, i.e., $d = 50$.