Hi,

I am new to probablity topic and learning it. I stuck in solving below questions, so need assistance.Please help me out in finding the way to solve these:-

Q1 - The probability of bomb hitting a bridge is 1/2 and 2 direct hits are required to destroy it.The least number of bombs required so that the probability of the bridge being destroyed is greater than 0.9 is :

Book Answer is - 7 bombs.

Q2 - Out of a pack of 52 cards one is lost; from the remainder of the pack 2 cards are drawn and are found to be spades.Find the chances that the missing card is a spade?

Book Answer is - 11/50

Q3 - seven white balls and three black balls are randomly placed in a row. Find the probability that the no 2 black balls are placed adjacent to each other ?

Book Answer is - 7/15

Any help would be greatly appreciated.

Thanks,

Ashish