Math Is Fun Forum

it is claimed that 90% of the children who were given flu jabs do not catch flu in the next six months following the jab. it is assumed that children catch flu independently of each other.

find the least interger r such that the probability of less than r children catching flu within the next 6 months is more than 3%. 

ans: 9

does anyone knows how to solve ∫ln(3-x²) dx ?   

I put $k in a bank savings account on the first day of each month. At the end of each month, interest is added to the account at a fixed rate of 0.5% of the total amount in the account. Assuming that i did not withdraw any money from the account, show that at the end of n months, i have

$(1.005k + 1.005^2k + 1.005^3k+......+1.005^nk)

find the minimum number of months I have to save so that at the end of which the total amount of money in the bank exceeds $100k.

five married couples are to be seated in a row of ten adjacent seats for a concert. in how many ways can they be seated if
(I) each couple must sit together
(II) all the men sit in a group while all the women sit together given that no husband sits next to his wife.

the answer is (I) 3840 and (II) 23040