Find the 19th term of the AP (1.2, 2.7, 4.2, ...).

Correct answer: 28.2

For an arithmetic progression, the nth term is aₙ = a + (n − 1)d. The first term is a = 1.2, and the common difference is d = 2.7 − 1.2 = 1.5. The next difference, 4.2 − 2.7, is also 1.5, confirming the AP. For n = 19, substitute into the formula: a₁₉ = 1.2 + (19 − 1)(1.5) = 1.2 + 18 × 1.5 = 1.2 + 27 = 28.2. Thus option D is correct. A common mistake is to multiply the difference by 19 rather than 18, which gives 29.7; that incorrectly counts one extra step because the first term already occupies position one. The decimal calculation and the index both support 28.2.