Question

The cost of 6 meters of ribbon is $15. How much ribbon could you buy for $20

Answer 1

Cost(C) $\propto$ Length (L)

$\implies\>C=KL$ where $K$ is a constant

When $C=15$

$L=6$

$\implies\>15=K(6)$

$K=\frac{15}{6}$

$C=\frac{15}{6}L$

$\implies\>L=\frac{6}{15}C$

When $C=20$

$L=\frac{6}{15}×20$

$=8\>meters$