=============================================================
Explanation:
Let's say the shed comes in 40 equal pieces. Each piece takes the same amount of time to assemble. Why am I picking 40? Because 8*5 = 40.
This will allow us to rewrite the fractions with a common denominator.
- 1/5 = 8/40 .... multiply top and bottom by 8
- 5/8 = 25/40 .... multiply top and bottom by 5
So Jack can build 8/40 of the shed in the same amount of time Kyle can build 25/40 of the shed.
Instead of writing fractions (which honestly are a pain to deal with), I'm going to write "8 pieces" and "25 pieces" to represent "8/40" and "25/40" respectively. Just keep in mind that there are 40 pieces total.
So again, Jack can assemble 8 pieces in the time it takes Kyle to assemble 25 pieces.
---------------
The ultimate goal is to have Kyle assemble 40 pieces while Jack puts together some unknown number of pieces (some number between 8 and 40). Let's say it's x.
We can then form this proportion
which simplifies or cleans up to
5/x = 25/40
-----------------
Let's solve for x using cross multiplication
8/x = 25/40
8*40 = x*25
320 = 25x
25x = 320
x = 320/25
x = 12.8
So in the time it takes Kyle to assemble all 40 pieces, Jack can put together 12.8 pieces of the shed. However, we can't have Jack put together some fractional piece, because each "piece" is as small as it gets. We can't get any smaller. It would be like saying a fractional part of an atom or a lego block.
So we'll round 12.8 down to 12.
Jack can assemble 12 pieces in the time it takes Kyle to assemble 40 pieces.
Let's then convert this back to fraction form
12 pieces = 12/40 of a shed = 3/10 of a shed.