1. ## probability question help

In a precision bombing attack there are 50% chance that any one bomb will strike the target. Two direct hits are required to destroy the target completely. How many bombs must be dropped to give a 99% chance or better of completely destroying the target?

A car hire firm has 2 cars which it sends out day by day. The number of demands for a car on each day is distributed as Poisson variate with mean 1.5.
calculate the proportion of days on which some demands are refused.

please explain to me how you proceed for each question

2. Originally Posted by mehn
In a precision bombing attack there are 50% chance that any one bomb will strike the target. Two direct hits are required to destroy the target completely. How many bombs must be dropped to give a 99% chance or better of completely destroying the target?

[snip]
Let X be the random variable "number of target strikes".

X ~ Binomial(n = ?, p = 1/2).

You require the smallest integer value of n such that $\Pr(X \geq 2) \geq 0.99 \Rightarrow \Pr(X \leq 1) < 0.01$.

3. Originally Posted by mehn
[snip]
A car hire firm has 2 cars which it sends out day by day. The number of demands for a car on each day is distributed as Poisson variate with mean 1.5.
calculate the proportion of days on which some demands are refused.

please explain to me how you proceed for each question

Calculate $\Pr(X > 2) = 1 - \Pr(X \leq 1)$.

4. thank you! =)

i have tried the first part but i'm stuck with

(0.5)^n(1+n)<= 0.01

i can't solve this... can u help me proceeding with this equation?!

5. Originally Posted by mehn
thank you! =)

i have tried the first part but i'm stuck with

(0.5)^n(1+n)<= 0.01

i can't solve this... can u help me proceeding with this equation?!
The simplest approach is to use trial and error. Does n = 3 work? n = 4? .....