Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
Use the middle of the NCERT range for Homo habilis, which is 725 cc. Homo erectus had about 900 cc, and Neanderthal man about 1400 cc.
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. cc, cc and cc.
Plan. Find the increase, divide by the earlier value, and multiply by .
Step 1. (a) per cent.
Step 2. (b) per cent.
Step 3. (c) times.
Answer: per cent; per cent; times.
Check. , the same as the ratio of the last answer.
Watch out. If you divide by the later value, you get a different number. The reference is always the earlier value.
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NCERT brain capacities: Homo habilis to cc, Homo erectus about cc, Neanderthal man about cc. A percentage increase is .