Final answer:
The total area of two joined and congruent parallelograms with base 11 cm and height 15 cm is 330 cm².
Step-by-step explanation:
To calculate the total area of two joined and congruent parallelograms, we would simply find the area of one and double it, as the two are identical.
The formula for the area of a parallelogram is base times height.
However, there seems to be a discrepancy in the measurements provided in the question.
Assuming the dimensions 11 cm and 15 cm are the base and height of one parallelogram, the area of one parallelogram would be 11 cm × 15 cm = 165 cm².
Since the parallelograms are congruent, the total area of the two parallelograms would be 165 cm² × 2 = 330 cm².
The additional base length of 18 cm seems unrelated to the calculation of the total area, unless there is further context missing.