Question

The actual length of a painting was $2m$. What is the length of the photograph if the scale used is $1mm:20cm$.

Answer 1

The actual length of the painting was $2m$ or $2\times 100=200cm$
[$\therefore$ $1m=100cm$]
Scale used in the painting $=1mm:20cm$
Hence, length of painting in photograph $=$ Scale $\times$ Actual Size
[Because Scale $=\frac{\text{size~drawn}}{\text{actual~size}}$]
$=\frac{1}{20}\times 200$
Therefore, the length of painting in photograph $=10mm$.