<prompt> A contraceptive X is used by 100 couples for continuous period of 2 years. During this period 20 women become pregnant despite using contraceptive X. What is the pearl index of contraceptive X?0.1 per HWY1 per HWY10 per HWY1000 per HWY  <response>: - The Pearl index is defined as the number of failures per 100 woman-years of exposure HWY. - This rate is given by the formula : - PI Total accidental pregnancies x 1200 Total months of exposure In given question: Total accidental pregnancies20 Total months of exposure100 couples x 24 months each2400 months PI 20 x1200 2400 10 per HWY 