Idea 14of 22Builds onAdd two columns to make a third
Ratios on a double number line
How do two number lines show a ratio?
Today you'll discover
- how the two lines line up
- how to skip-count both lines
- how to read one amount from the other
Think first2 scoops of mix for every 5 cups of water
2 scoops lines up with 5 cups of water. What lines up with 4 scoops?
Decide first, then press Next. Read straight down from a tick.
Two number lines, scoops of mix on top and cups of water below, both starting at 0. First only 2 and 5 are marked, joined by a dashed line. Then ticks at 4 and 10, 6 and 15, 8 and 20, with arcs marked plus 2 on top and plus 5 below. Then the 8 and 20 tick is ringed. The last step shows cans of red and white paint.
See the whole ideathe big idea and the key word, in one place
The big idea
A double number line lines up the two amounts of a ratio, tick by tick.
Compare themA ratio table and a double number line hold the same pairs. The table lists them in columns; the lines space them out, so in-between amounts have a place.
Easy to get wrongLine up the ticks. 2 scoops must sit right above 5 cups, or every pair you read is wrong.
Key word
- double number line
- two number lines, one above the other, where the ticks that line up are pairs of equivalent ratios
Ready to use it?
- Draw a double number line for a ratio.
- Read an equivalent ratio off the two lines.