SAT Math Question of the Day

Math Category: Combinations:

Q: In the "New Diet" promoted by Dr. Quack, a person can choose any 3 items from the following list of acceptable foods: Asparagus, Beans, Chicken, Donut, Eggplant, or Fish to make a complete meal. How many different combinations of meals can be made?

  1. 20
  2. 22
  3. 24
  4. 26
  5. 28

UNANSWERED.

The correct answer is A.

A: The correct answer is 20.

There are 6 possible food items: A, B, C, D, E, and F. For the first food item, it can be any of these 6 foods. For the second food item, it can be any of the remaining 5 foods. For the third food item, it can be any of the remaining 4 foods. Since order doesn't matter, we divide by the number of ways 3 items can be arranged ... that is 3! or 3 × 2 × 1.
6 × 5 × 4 / 3 × 2 = 20

You can also try listing the possible combinations. Remember that order does not matter. Try to make the list in alphabetical order, so that you don't forget to list one of the combinations.

  1. A B C
  2. A B D
  3. A B E
  4. A B F
  5. A C D
  6. A C E
  7. A C F
  8. A D E
  9. A D F
  10. A E F
  11. B C D
  12. B C E
  13. B C F
  14. B D E
  15. B D F
  16. B E F
  17. C D E
  18. C D F
  19. C E F
  20. D E F