Question

If a phone company charges $ 0.40 for the first minute and $ 0.30 for each additional minute for a long-distance call, how much will a 19 -minute long-distance call cost?

Answer 1

The given situation forms an AP.
Therefore, a = 0.4 and d = 0.3.
Hence, for the 19th minute,
a + 18d = 0.4 + 18×0.3 = 0.4 + 5.4 = 5.8 dollars.
hence proved.