Brain Teasers
Multiplying Mice
Marco's Uncle Oscar gave him 2 mice, which he named Whiskers and Oscar. But Marco discovered that he made a big mistake. Oscar should have been named Oscarella. She just had 8 babies - 4 males and 4 females!
"Ten mice aren't so many," said Marco to his mother. "And they're cute."
"Yes," said his mother, "but these cute baby mice can breed when they are 6 weeks old. The babies are born after 3 weeks of pregnancy."
If each female mouse has only 1 litter and all the litters have 8 babies, half males and half females, how many mice will Marco have in 18 weeks?
"Ten mice aren't so many," said Marco to his mother. "And they're cute."
"Yes," said his mother, "but these cute baby mice can breed when they are 6 weeks old. The babies are born after 3 weeks of pregnancy."
If each female mouse has only 1 litter and all the litters have 8 babies, half males and half females, how many mice will Marco have in 18 weeks?
Hint
Make a time chart.Remember, the question asks you to assume that each female mouse has only 1 litter.
Answer
After 18 weeks there will be a total of 170 mice.Each of the 4 young females just born will have 8 babies in 9 weeks, making 32 babies; 16 of the babies will be male and 16 will be female.
The 16 females in those litters will have 8 * 16 = 128 babies.
In 18 weeks, Marco will have the 2 original mice (Whiskers and Oscarella) + 8 babies + 32 babies + 128 babies = 170 mice.
That's a lot of mice!
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Comments
Ugh forgot to add in the parents. Great teaser!
so these mice only breed once in their lifetimes?
If the litters are born 'after' 3 weeks, won't it be slightly 'after' 18 weeks before the 170 figure is reached?
Just like Rukia, I also wonder if mice breed only once in their lifetimes.
Also the teaser said these cute baby mice "can" breed when they are 6 weeks old. They can breed but I'm not sure if they "will" indeed breed immediately when they are 6 weeks old!
Also the teaser said these cute baby mice "can" breed when they are 6 weeks old. They can breed but I'm not sure if they "will" indeed breed immediately when they are 6 weeks old!
Have to account for the mice killing each other though. Those kinds of circumstances they kill each other big time competing for the territory.
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