Question

you want to determine how many minutes are in one day. what choice goes in the green box?
1 day

?
hint: make sure your units are cancelling!
24 hours
1 hour
60 minutes
1 day

Explanation:

Step1: Identify unit conversion start

We start with 1 day, and need to convert days to hours first. The conversion factor for days to hours is $\frac{24\ \text{hours}}{1\ \text{day}}$, so the denominator of the first conversion fraction (green box) must cancel the "day" unit.

Step2: Match the required denominator

To cancel the "1 day" term, the green box (denominator of the first conversion factor) must be 1 day, which allows us to proceed to convert hours to minutes next.

Answer:

1 day