      #### Exercise machine arccos

In a gym there is an exercise machine that consists of an inclined plane (2 meters long) leaning against a wall (see the schematic of the machine in the figure). Initially, the base of the plane was placed at a distance $x = 1 \ m$ from the wall, and in this case, the plane is inclined at an angle of $\theta=\dfrac{\pi}{3} \ rad$ to the floor. The steepness is given by the function $$\theta (x)= \arccos \left( \dfrac{x}{2}\right).$$ Estimate, using the differential, what is the new steepness of the machine if the distance from the base of the plane to the wall is increased to $x = 1.05 \ m$.

# Complements of differential calculus in real numbers

Reasoning
13 #### In search of Big Macs

Jon is an American guy who loves Big Macs. While on a trip around the world, he eats eight Big Macs: two in Germany, one in the United States, two in Switzerland, and three in India. Assuming that the prices of the Big Mac are: In Germany 3.59 €, in the United States 4.59 €, in Switzerland 5.99 € and in India 1.77 €. a) What was Jon's total expenditure on Big Macs during his vacation? b) If his flight was canceled, Jon would stay in the United States. In the United States, how much would he spend on the same number of Big Macs?
# Decimal fractions
# Units & rounding

Training
5  #### The population

The population of a town is 20.000 citizens. From them 8.206 are men. Men are 426 fewer than women. How many children are living in the town?

# Operations with natural numbers

Training
5      #### Distributive Property in Algebraic Expressions_2

Match the following algebraic expressions: 1. $4(x-2)-3+x$ 2. $3(x-2)-(x-3)$ 3. $-2(-x+2)+3(x+2)$ 4. $-(x-2)+3(x-2)$ to its equivalent simplified expression, by writing the number of expression to the right

# Terms with variables

Training
8 #### Granit prism

Calculate the volume of the granit block. Round the result in m³ to two decimal places.

# Cubes & cuboids

Training
8 #### Granit bench

Calculate the weight of the sitting part of a granit bench. The sitting part of the bench has the following dimensions: width 43 cm, height 13 cm, length 180 cm. The density of granit is 2600 kg/m³. Give the result rounded to the nearest whole in kilograms.

# Cubes & cuboids

Reasoning
8