Lesson eLearning

In a population where 500 women use a copper IUD (typical‑use failure rate 0.6 % per year) and another 500 women use male condoms (typical‑use failure rate 18 % per year) for one year, how many unintended pregnancies are expected among all 1000 women and how many pregnancies could be avoided if all 1000 women switched to copper IUDs?

medium 2 marks Class 12 · Biology · Reproductive Health
Answer
93 pregnancies expected; 87 pregnancies avoided

The correct answer is 93 pregnancies expected; 87 pregnancies avoided — Subtract to find avoided pregnancies: 93 − 6 = 87.

Step-by-step solution

  1. Convert 0.6 % to decimal: 0.006.
  2. Calculate pregnancies from copper IUD: 500 × 0.006 = 3.
  3. Convert 18 % to decimal: 0.18.
  4. Calculate pregnancies from condoms: 500 × 0.18 = 90.
  5. Add both: 3 + 90 = 93 pregnancies expected.
  6. If all 1000 women used copper IUD: 1000 × 0.006 = 6 pregnancies.
  7. Subtract to find avoided pregnancies: 93 − 6 = 87.
Common mistake: Adding failure rates instead of calculating actual pregnancies

Concept tested: Contraceptive failure rates

Published · How this solution was prepared and checked

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