Question

Jamal is making two paintings using canvases that are similar rectangles. The length of the smaller canvas is 3 ft and the width is 5 ft.
What is the length of the larger canvas if the width is 10 ft?

Answer 1

Let's start with what we know:

Smaller canvas:
Length ($L_{1}$) = 3ft
Width ($W_{1}$) = 5ft

Larger canvas:
Length ($L_{2}$) = ?
Width ($W_{2}$) = 10ft

Since these are similar rectangles, we can cross-multiply to calculate the missing length. Here's that formula:

$\frac{ L_{1} }{ L_{2} } = \frac{ W_{1} }{ W_{2} }$
So let's plug it all in from above:

$\frac{ 3 }{ L_{2} } = \frac{ 5 }{ 10 }$
Now we cross multiply by multiplying the top-left by the bottom-right and vice versa:

$(3)(10) = (5)(L_{2})$
$30 = 5L_{2}$
Now divide each side by 5 to isolate $L_{2}$

$\frac{30}{5} = \frac{ 5L_{2}}{5}$
The 5s on the right cancel out, leaving us with:

$6 = L_{2}$

So the length of the larger canvas is 6 ft

Answer 2

It's not as complicated as you think. The smaller rectangle is 3ft with a width of 5ft. It's asking what the length of the larger canvas is if the width is 10ft. So you pretty much just do 10/5 which is 2 then you multiply 3ft by 2 and you get 6ft.

If you need any help just ask :)

-John