Question

Suppose triangle ABC ~ triangle GHI with scale factor 3:5, and AB=9, BC=18 and AC=21. What is the perimeter of triangle GHI?

Answer 1

`color(white)(xxxx)80`

Explanation:

`color(white)(xx)|AB|/|GH|=3/5`
`=>color(red)9/|GH|=3/5`
`=>|GH|=15`

`color(white)(xx)|BC|/|HI|=3/5`
`=>color(red)18/|HI|=3/5`
`=>|HI|=30`

`color(white)(xx)|AC|/|GI|=3/5`
`=>color(red)21/|GI|=3/5`
`=>|GI|=35`

Therefore perimeter is:
`color(white)(xx)|GH|+|HI|+|GI|=15+30+35`
`color(white)(xxxxxxxxxxxxxxx)=80`