Exams

When the European union formed nations began to cooperate on law enforcement. The European Union is set up with the aim of ending the frequent and bloody wars between neighbours, which culminated in the Second World War.

As of 1950, the European Coal and Steel Community begins to unite European countries economically and politically in order to secure lasting peace. The six founding countries are Belgium, France, Germany, Italy, Luxembourg and the Netherlands. The 1950s are dominated by a cold war between east and west.

The historical roots of the European Union lie in the Second World War. Europeans are determined to prevent such killing and destruction from ever happening again.

Two series alternate here, with every third number following a different pattern.
In the main series, 4 is added to each number to arrive the next.
In alternate series, 5 is subtracted from each number t arrive the next number.
Here in the main series 
3 + 4 = 7
7 + 4 = 11
11 + 4 = 15
15 + 4 = 19

In alternate series 
24 - 5 = 19
19 - 5 = 14...

The given math puzzle follows a logic that,

1 + 4 = 5 => 1 x 4 + 1 = 5

2 + 5 = 12 => 2 x 5 + 2 = 12

3 + 6 = 21 => 3 x 6 + 3 = 21

Similarly,

8 + 11 = > 8 x 11 + 8 = 96.

The Opium Wars were two wars in the mid-19th century involving Anglo-Chinese disputes over British trade in China and China’s sovereignty. The disputes included the First Opium War (1839–1842) and the Second Opium War (1856–1860).

4, 14, 24, 34, 44, 54, 64, 74, 84, 94 => has 11 number of (4's)
40, 41, 42, 43, 45, 46, 47, 48, 49 => has 9 number of (4's)
So, totally (11 + 9 = 20) number of 4's in 1 to 100.