Coins

Edmund had saved a certain number of 0.5-euro coins. He placed the coins in a single layer in a square. He had 4 coins left. When he wanted to build a square with one more row, he was missing 23 coins.
How many euros does he have?

Final Answer:

n =  86.5 Eur

Step-by-step explanation:

$$\begin{gathered} n=0.5\cdot x \\ x\cdot x+4=(x+1)(x+1)-23 \\ 4=2x+1-23 \\ x=13 \\ n=0.5\cdot (x\cdot x+4)=0.5\cdot (13\cdot 13+4)=86.5\text{Eur} \end{gathered}$$

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