3
Month 4 starts out with two rabbits (the number under month 3) one of which is mature (the number under month 2). During month 4 the mature rabbit gives birth to another baby. The chart shows the total of three rabbits at the end of month 4.
N | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
Females | 1 | 1 | 2 | 3 | ||||||
* | ** |
* — — Mature females at start of month 4 ** — — Total females at start of month 4
The total number of female rabbits at the start of a month is shown under the previous month in the chart. The number of mature rabbits (which give birth during that month) is the number shown under the second previous month.
How many mature female rabbits are there at the start of month 5?