Postage stamps 2

Pavel collects postage stamps. He has the same number of one-crown and three-crown stamps in his collection, and he also has five-crown stamps, which are twice as many as one-crown stamps. The sum of the prices listed on all the stamps is 448 CZK. How many stamps does Pavel have in total in his collection?

Correct answer:

n =  128

Step-by-step explanation:

$$\begin{gathered} a=b \\ c=2a \\ 448=1a+3b+5c \\ 448=1a+3a+5\cdot 2a \\ 448=1\cdot a+3\cdot a+5\cdot 2\cdot a \\ 14a=448 \\ a=\frac{448}{14}=32 \\ a=32 \\ b=a=32 \\ c=2\cdot a=2\cdot 32=64 \\ n=a+b+c=32+32+64=128 \end{gathered}$$

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