Questions

The letter 'O'.

At least one black can be chosen in two ways from each box:
Now, probability of choosing at least one black ball from first box 

= 1/2 × [ (2C1× 2C1)/4C2 + 2C2/ 4C2 ]= 5/12

Probability of choosing at least one black ball from 2nd box
= 1/2 × [(4C1×12C1)/16C2 + 4C2/ 16C2] = 9/40

Final probability

= 5/12 + 9/40 = (50 + 27)/120 = 77/120

There are 60 minutes in an hour.

In ¾ of an hour there are (60 × ¾) minutes = 45 minutes.

In ¾ of an hour there are (60 × 45) seconds = 2700 seconds.

Siren sounds for every 5 seconds.

In 2700 seconds = 2700/5 = 540 times.

The count start after the first sound, the Siren will sound 541 times in ¾ of an hour.

The Communist Government of Yugoslavia had kept itself free from the Soviet Union almost from the beginning . Yugoslavia was one of the founders of the Non-Aligned Movement. It was a fedaration of 6 republics. In four of these republics, the rule of the communist parties came to an end in 1990. By 1992,Yugoslavia broke up into five independent states-the new states of yugoslavia comprising Serbia and Montenegro, Croatia, Macedonia, Slovenia and Bosnia-Herzegovina.

The given statement is clearly true.