11 Formalizzare problemi ESERCIZI PRACTICE WITH CLIL Problems Different ways can be followed in order to formalize a problem: by using an expression, a table, a function, or through basic geometric objects. We will submit an arithmetical problem to you: it shall be formalized by a graph. «Four persons (Mr. Whites, Mr. Blacks, Mr. Greens, Mr. Reds) are on a holiday together and they decide to establish a petty cash fund for their general expenses. Each one of them shall contribute with 200 . Nevertheless, some expenses have already occurred: Mr. Whites (B) has already spent 50 for general expenses; moreover, he has lent 75 to Mr. Greens (V) who could not have his money changed; then a 40-Euro full of gasoline was made, which was paid in advance by Mr. Blacks (N) with 15 and by Mr. Reds with 25 ; at the end, Mr. Blacks (N) has lent 10 to Mr. Reds and 40 to Mr. Whites. To make their accounts balanced among them how many Euros will each of them have to put in the petty cash (C)? It is appropriate to represent the situation into two graphs. In the first, we will report the money exchanges already occurred: the arrow shows the relation having already lent money to . The number on the arrow specifies how many Euros were already given away. Complete the graph, which has been filled in with N s operations (Mr. Blacks) only. N 40 15 10 B V R C Now, each of them will put money in the petty cash fund in order to balance the debts among the four friends, too. For instance, Mr. Whites, who like all others should contribute altogether with 200 , has already paid in 50 and other 75 will be deposited, in his place, by Mr. Greens to whom he was claiming the credit; on the contrary, he shall add 40 which he borrowed from Mr. Blacks. Therefore, overall: euros that B shall put in the petty cash = 200 75 50 + 40 = 115 Complete the graph with the Euros that each one of them shall deposit in the petty cash. The arrow shows the relation money due to the petty cash , and the number on the arrow specifies the euros that shall be paid in. 455