Complex Unit Rates

How the lesson starts: Complex Unit Rates

Tilly trains
Hi there! Tilly the tortoise is training for the Great Garden Race. She walks 2 miles in 1/3 hour. Her coach wants her speed in miles per hour. But she didn't walk a whole hour! How can we find it?
Keep walking!
A unit rate is the amount for 1 whole unit, here 1 whole hour. Every 1/3 hour adds 2 miles. 1/3 hour: 2 miles. 2/3 hour: 4 miles. 3/3 hour, a whole hour: 6 miles. So Tilly walks 6 miles per hour.
The rule: divide
Here's the shortcut. Miles per hour means miles ÷ hours. On race day, Tilly walks 3/2 mile in 1/4 hour. So (3/2) ÷ (1/4). Flip and multiply: 3/2 × 4/1 = 12/2 = 6. Watch out: flip only the 1/4 you divide by, not the miles.