Legs

Cancer has five pairs of legs, and the insect has six legs. Sixty animals have a total of 500 legs. How much more are cancers than insects?

Correct answer:

d =  10

Step-by-step explanation:

$$\begin{gathered} 5\cdot 2\cdot r+6\cdot h=500 \\ r+h=60 \\ 6h+10r=500 \\ h+r=60 \\ Row2-\frac{1}{6}\cdot Row1\to Row2 \\ 6h+10r=500 \\ -0.67r=-23.33 \\ r=\frac{-23.33333333}{-0.66666667}=35 \\ h=\frac{500-10r}{6}=\frac{500-10\cdot 35}{6}=25 \\ h=25 \\ r=35 \\ d=r-h=35-25=10 \end{gathered}$$

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