The additional payment for each day- is fixed.
Hence the payments to be made are in G.P. .
Here in this problem
Charges for first day
= First term of AP (a)
∴ a = Rs.10
Additional charge for each day = Rs.2
∴ Common difference (d) = 2/-
∴ The A.P. is 10, 12, 14, 16, …………….. (15 terms)
The total amount to be paid for 15 days is S15 = ?
So he has to pay Rs.360 for 15 days parking.