In a salad recipe, the ratio of carrots to broccoli must remain constant. The table below shows some possible combinations of carrots and broccoli.

Salad Ingredients
Carrots
Broccoli
3
9
4
12
6
18
7
21

If only whole vegetables can be used, what is the fewest number of vegetables that can be used to make this salad?
1
3
4
12

1 answer

To determine the fewest number of vegetables that can be used to maintain the constant ratio of carrots to broccoli, we first assess the given combinations of vegetables:

  • 3 carrots and 9 broccoli (total = 12)
  • 4 carrots and 12 broccoli (total = 16)
  • 6 carrots and 18 broccoli (total = 24)
  • 7 carrots and 21 broccoli (total = 28)

Next, we calculate the ratio of carrots to broccoli for each combination:

  • For 3 carrots and 9 broccoli, the ratio is \( \frac{3}{9} = \frac{1}{3} \)
  • For 4 carrots and 12 broccoli, the ratio is \( \frac{4}{12} = \frac{1}{3} \)
  • For 6 carrots and 18 broccoli, the ratio is \( \frac{6}{18} = \frac{1}{3} \)
  • For 7 carrots and 21 broccoli, the ratio is \( \frac{7}{21} = \frac{1}{3} \)

All combinations maintain the same ratio of \( \frac{1}{3} \), meaning for every 1 carrot, there are 3 broccolis.

To find the fewest number of whole vegetables combined, we can represent the number of carrots as \( c \) and the number of broccolis as \( b \), adhering to the ratio \( \frac{c}{b} = \frac{1}{3} \), or rewritten as \( b = 3c \).

The total number of vegetables (carrots + broccoli) becomes:

\[ c + b = c + 3c = 4c \]

To minimize \( c + b \), we must select the smallest whole number for \( c \), which is 1.

Substituting \( c = 1 \):

\[ b = 3(1) = 3 \]

Thus, the total number of vegetables is:

\[ c + b = 1 + 3 = 4 \]

Therefore, the fewest number of vegetables that can be used to make the salad is 4.