You are given an arithmetic progression (an), the difference of which is 1.6. a1 = -1 find a11.

To find the eleventh member a11 of this arithmetic sequence, we use the formula for the nth member of the arithmetic progression an = a1 + (n – 1) * d, where a1 is the first member of the arithmetic progression, d is the difference of the arithmetic progression.

By the condition of the problem, the first member a1 of this arithmetic sequence is -1, and the difference d of this progression is 1.6.

Substituting these values, as well as the value n = 11 in the formula for the nth term of the arithmetic progression, we get:

a11 = -1 + (11 – 1) * 1.6 = -1 + 10 * 1.6 = -1 + 16 = 15.

Answer: a11 = 15.