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Lemur [1.5K]
3 years ago
10

Amy has four more 20c coins than 5c coins. The total value of all her 20c and 5c is $3.80. How many 5c coins does Amy have?

Mathematics
1 answer:
skelet666 [1.2K]3 years ago
6 0

Answer:

Amy has 12 5¢ coins

Step-by-step explanation:

Let <em>x</em> represent 20¢ coins and <em>y</em> represent 5¢ coins.

Amy has four more 20¢ coins than 5¢ coins. Hence:

x=y+4

And the total value of all her coins is $3.80. Thus:

0.2x+0.05y=3.8

This yields a system of equations:

\displaystyle \begin{cases} x=y+4 \\ 0.2x+0.05y=3.8\end{cases}

We can solve by substitution. Substitute the first equation into the first:

\displaystyle 0.2(y+4)+0.05y=3.8

Distribute:

\displaystyle 0.2y+0.8+0.05y=3.8

Combine like terms:

\displaystyle 0.25y = 3

And divide both sides by 0.25. Hence:

y=12

Thus, Amy has 12 5¢ coins.

Using the first equation:

x=y+4

Substitute:

x=(12)+4=16

Thus, Amy has 16 20¢ coins.

In conclusion, Amy has 12 5¢ coins and 16 20¢ coins.

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