4/5 = 8/? = ?/15 = ?/20 = 20/?

1 answer

To solve for the missing values in the given proportion, we can use the concept of equivalent ratios. Let's denote the missing values by \( a, b, c, \) and \( d \) respectively.

Given proportion:
\[ \frac{4}{5} = \frac{8}{a} = \frac{b}{15} = \frac{c}{20} = \frac{20}{d} \]

First, solve for \( a \) using the ratio \( \frac{4}{5} = \frac{8}{a} \):

\[ \frac{4}{5} = \frac{8}{a} \]
\[ 4a = 5 \cdot 8 \]
\[ 4a = 40 \]
\[ a = 10 \]

So, \( a = 10 \). Therefore:
\[ \frac{4}{5} = \frac{8}{10} \]

Next, solve for \( b \) using the ratio \( \frac{4}{5} = \frac{b}{15} \):

\[ \frac{4}{5} = \frac{b}{15} \]
\[ 4 \cdot 15 = 5b \]
\[ 60 = 5b \]
\[ b = 12 \]

So, \( b = 12 \). Therefore:
\[ \frac{4}{5} = \frac{12}{15} \]

Next, solve for \( c \) using the ratio \( \frac{4}{5} = \frac{c}{20} \):

\[ \frac{4}{5} = \frac{c}{20} \]
\[ 4 \cdot 20 = 5c \]
\[ 80 = 5c \]
\[ c = 16 \]

So, \( c = 16 \). Therefore:
\[ \frac{4}{5} = \frac{16}{20} \]

Finally, solve for \( d \) using the ratio \( \frac{4}{5} = \frac{20}{d} \):

\[ \frac{4}{5} = \frac{20}{d} \]
\[ 4d = 5 \cdot 20 \]
\[ 4d = 100 \]
\[ d = 25 \]

So, \( d = 25 \). Therefore:
\[ \frac{4}{5} = \frac{20}{25} \]

So the complete proportion with the missing values filled in is:

\[ \frac{4}{5} = \frac{8}{10} = \frac{12}{15} = \frac{16}{20} = \frac{20}{25} \]