Journey to grandma

Daniel traveled to Grandma. He traveled 100 km, halfway by train, one quarter by bus, one-tenth by bicycle, and the rest by car. How many km did he travel by car?

Final Answer:

x =  85 km

Step-by-step explanation:

$$\begin{gathered} a=100\text{km} \\ s=\frac{1}{2}-\frac{1}{4}-\frac{1}{10}=\frac{10}{20}-\frac{5}{20}-\frac{2}{20}=\frac{10-5-2}{20}=\frac{3}{20}=0.15 \\ b=s\cdot a=\frac{3}{20}\cdot 100=\frac{3\cdot 100}{20}=\frac{300}{20}=15\text{km} \\ x=a-b=100-15=85\text{km} \end{gathered}$$

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