Two dice are thrown at the same time.

It is given that two dice are thrown at the same time.

We have to find the probability of getting different numbers on both dice.

Total number of possible choices in rolling a dice = 6

Total number of possible choices in rolling two dice [Using multiplication rule]

Probability of getting same number if two dice are thrown

$\mathrm{P}($ Same Number $)=\frac{6}{36}$

Probability of getting different number if two dice are thrown

$=1-\mathrm{P}($ Same Number $)$

     $=1-\frac{6}{36}$

$=\frac{30}{36}$

$=\frac{5}{6}$

OR

It is given that a coin is tossed two times.

Therefore, sample space is given by,

{HH, HT, TH, TT}

Let E be the event of getting two heads. I.e., E = {HH}

Then, probability of getting atmost one head is given by

$P\left(E^{\prime}\right)=P(H T$ or $T H$ or $T T)=1-P(E)=1-P(H H)=1-\frac{1}{4}=\frac{3}{4}$