# probabiity

• May 21st 2008, 12:58 PM
key
probabiity

When Bill bowls, he can get a strick 60% of the time. How many times more likely is it for Bill to bowl at least three strikes out of four tries as it is for him to bowl zero strikes out of four tries. Round to nearest whole number.

I gpt 47 times more likely. Is that correct.

Thanks
• May 21st 2008, 01:12 PM
janvdl
Quote:

Originally Posted by key

When Bill bowls, he can get a strick 60% of the time. How many times more likely is it for Bill to bowl at least three strikes out of four tries as it is for him to bowl zero strikes out of four tries. Round to nearest whole number.

I gpt 47 times more likely. Is that correct.

Thanks

He has a probability of 0,6 to bowl a strike.

The chances that he gets a strike AT LEAST 3 out of 4 times he bowls:

$\displaystyle {4 \choose 3} \left( \frac{3}{5} \right)^{3} \left( \frac{2}{5} \right)^{1}$ $\displaystyle + {4 \choose 4} \left( \frac{3}{5} \right)^{4} \left( \frac{2}{5} \right)^{0} = \frac{216 + 81}{625} = 0,4752$

The chances that he does not score a strike at all:

$\displaystyle {4 \choose 0} \left( \frac{3}{5} \right)^{0} \left( \frac{2}{5} \right)^{4} = \frac{16}{625} = 0,0256$

I get 18,56 times more likely.