The probability of scoring $70$ marks in a $100$ marks test is ...........

In cricket,Rohit hits a century in $4$ innings out of $10$ innings. Find the probability that he did not hit a century.

The probability of a certain event is ........

The probability of the event 'the sun rises in the east' is .............

$A$ company selected $4000$ households at random and surveyed them to find out a relationship between income level and the number of television sets in a home. The information so obtained is listed in the following table:

Monthly income (in Rs)	$0$ Televisions	$1$ Television	$2$ Televisions	Above $2$ Televisions
$< 10000$	$20$	$80$	$10$	$0$
$10000-14999$	$10$	$240$	$60$	$0$
$15000-19999$	$0$	$380$	$120$	$30$
$20000-24999$	$0$	$520$	$370$	$80$
$25000$ and above	$0$	$1100$	$760$	$220$

Find the probability of a household earning $Rs. 25000$ and more per month and owning $2$ televisions.

Can the experimental probability of an event be a negative number? If not,why?