[求助]problem solving

yahoo750

I n a certain animal population, for each  of the fist  3 month of life,the probability that an animal will die at that month is 1/10. For a group of 200 newborn members of the population, approximately how many would be expected to survive during the first 3 months of life?
Could one help me, please.[em10]

passerr

200*(1-1/10)^3

Is it right?

yahoo750

Thank you, but I'm sorry to tell you that the answer is wrong. the correct answer is 146.I don't know how to get the answer.

isenetlab

??
200*(1-1/10)^3=146
yahoo75, what r u thinking?

孤注一掷

让我用最笨的方式来说吧:
By the end of first month, there are 200-200*1/10=180 left;
By the end of second month, there are 180-180*1/10=162 left;
By the end of third month, there are 162-162*1/10=145.8 left, so the answer is 146.

yahoo750

I've made it out at last! Thank you all of you!