Three populations have these shares in the pre-reproductive, reproductive and post-reproductive…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Three populations have these shares in the pre-reproductive, reproductive and post-reproductive groups.
Population X: , and the rest. Population Y: , and the rest. Population Z: , and the rest.
- What is the post-reproductive share of Z?
- Which population is expanding? Use the rule of the lesson.
- Which is declining? Which is stable?
Need a reminder? The key ideaShow
The sex ratio is the number of females for every males, . An age pyramid has a pre-reproductive, a reproductive and a post-reproductive group. A triangle means expanding, a bell means stable and an urn means declining.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. X: . Y: . Z: .
Plan. Find the rest. Then compare the pre-reproductive and the reproductive shares.
Step 1. (a) .
Step 2. (b) For X, points, more than , so X is expanding.
Step 3. (c) For Y, points, so Y is stable. For Z, points, so Z is declining.
Answer: ; X; Z is declining and Y is stable.
Check. The shares of X are , and those of Y are .
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