A recipe for stir fry calls for 5 cups of rice for every 4 cups of veggies. Suppose a restaurant is making a large batch of stir fry using 20 cups of veggies. How much rice would they need?

Start by labeling the double number line with the cups of veggies and cups of rice that the recipe calls for.
Veggies (cups)
0
4
Rice (cups)
0
5
Great job!
To find how many cups of rice they’d need for 20 cups of veggies, it can be helpful to first find the unit rate, or the amount of rice needed for 1 cup of veggies. Partition the number line to find the number of cups of rice needed for every 1 cup of veggies.
Veggies (cups)
0
4
Rice (cups)
0
5
Excellent!
Label the bottom number line to find the number of cups of rice the restaurant would need for 1 cup of veggies.
Veggies (cups)
0
1
2
3
4
Rice (cups)
0
5

1 answer

To find the unit rate of rice per cup of veggies, we can start with the recipe's ratio of rice to veggies: 5 cups of rice for every 4 cups of veggies.

First, we can determine how much rice is needed for each cup of veggies:

  1. From the recipe ratio, we know:

    • 4 cups of veggies corresponds to 5 cups of rice.
  2. To find the amount of rice needed for 1 cup of veggies, we can set up a proportion: \[ \frac{5 \text{ cups of rice}}{4 \text{ cups of veggies}} = \frac{x \text{ cups of rice}}{1 \text{ cup of veggies}} \]

  3. By cross-multiplying, we find: \[ 4x = 5 \]

    \[ x = \frac{5}{4} \text{ cups of rice} \]

So, we find that for 1 cup of veggies, \( \frac{5}{4} \) cups of rice are needed.

Next, we can extend this to find out how much rice is needed for 20 cups of veggies:

  1. If 1 cup of veggies requires \( \frac{5}{4} \) cups of rice, then for 20 cups of veggies: \[ \text{Rice needed} = 20 \text{ cups of veggies} \times \frac{5}{4} \text{ cups of rice per cup of veggies} \]

  2. Calculating this gives: \[ = 20 \times \frac{5}{4} = \frac{100}{4} = 25 \text{ cups of rice} \]

In summary, the restaurant would need 25 cups of rice for 20 cups of veggies.

Here's a representation of your double number line:

Veggies (cups)

0     1     2     3     4
0     5.   10    15    20

Rice (cups)

0     5     10    15    20
  • For 0 cups of veggies, you need 0 cups of rice.
  • For 4 cups of veggies, you need 5 cups of rice.
  • For 1 cup of veggies: \( \frac{5}{4} \) cups of rice.
  • For 2 cups of veggies: \( 2.5 \) cups of rice.
  • For 3 cups of veggies: \( 3.75 \) cups of rice.
  • For 20 cups of veggies: 25 cups of rice.