The answer is A: 5

- The number 5 when squared is: \(5^2\) = 25

- It is increased: \(25:5=5=500\%\)

The answer is C: 21(cm)

The answer is C) 21 centimeters.

The answer is A) 5 litres.

- There is: \(12\cdot\dfrac{3}{4}=9\left(litres\right)\) at first.

- After 4 litres has been poured out of it, it contains: \(9-4=5\left(litres\right)\)

The answer is B: 2/5

- There are 5 circles. The middle circle is full shaded and there are a quarter shaded in the 4 other circles, so that there are: 1 + 4 * 1/4 = 2 (circles shaded)

- The ratio = 2:5 = 2/5 (B)

There are: 10 * 10 * 10 * 10 * 10 = 100000 pieces of paper after the last cutting

The answer is C: 1009

- The three-digit number is: 999 / The two-digit number is: 10

The answer is C: 34 days.