Mackerel 6531

Mackerel costs m euros. If you buy mackerel and 20 sardines, you will pay double. How much will you pay for:

(a) mackerel and 40 sardines
(b) three mackerel and 80 sardines

Correct answer:

a = 3m
b = 7m

Step-by-step explanation:

$$\begin{gathered} m+20s=2m \\ 20s=m \\ s=m/20 \\ a=m+40s=m+40/20m \\ a=3m \end{gathered}$$

$$\begin{gathered} b=3m+80\cdot m/20=3m+4m \\ b=7m \end{gathered}$$

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