Siblings

48 children took part in the school trip. Six of them were there with one sibling, nine children were there with two siblings, and four with three siblings. The others did not have siblings on the trip. After returning, their parents were waiting for the children to take them home by car. Each family was left in one car. How many cars were waiting for the children to arrive?

Correct answer:

n =  36

Step-by-step explanation:

$$\begin{gathered} a=6/2=3 \\ b=9/3=3 \\ c=1 \\ d=48-(2\cdot a+3\cdot b+4\cdot c)=48-(2\cdot 3+3\cdot 3+4\cdot 1)=29 \\ s=2\cdot a+3\cdot b+4\cdot c+1\cdot d=2\cdot 3+3\cdot 3+4\cdot 1+1\cdot 29=48 \\ n=a+b+c+d=3+3+1+29=36 \end{gathered}$$

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