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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