Praxis Core Academic Skills for Educators: Mathematics (5733)Number and QuantityHard
A chef is adjusting a recipe for a large catering event. The original recipe calls for 1 1/4 teaspoons of salt. If the chef needs to make 3 1/2 times the original recipe, how much salt, in teaspoons, is needed?
- A4 3/8 teaspoons
- B5 1/4 teaspoons
- C3 5/8 teaspoons
- D4 1/2 teaspoons
Show answer & explanationAnswer & explanation
Correct answer: A. 4 3/8 teaspoons
Convert both mixed numbers to improper fractions: 1 1/4 = 5/4 and 3 1/2 = 7/2. Then multiply the improper fractions: (5/4) * (7/2) = 35/8. Convert the improper fraction back to a mixed number: 35/8 = 4 with a remainder of 3, so 4 3/8 teaspoons.
Why the other options are wrong
- B. Incorrect calculation, possibly from incorrectly converting 3 1/2 to 4 1/2 before multiplying.
- C. Incorrect calculation, perhaps from adding instead of multiplying or a multiplication error.
- D. Incorrect calculation, possibly from rounding or a simplification error.
Multiplying Mixed Numbers
To multiply mixed numbers, first convert each mixed number into an improper fraction. Then, multiply the numerators together and multiply the denominators together. Finally, simplify the resulting improper fraction back into a mixed number or simplest form.
- A mixed number is a whole number and a fraction.
- An improper fraction has a numerator greater than or equal to its denominator.
- Multiplying fractions involves multiplying numerators and denominators straight across.
Memory trick: Improper fractions first, then multiply straight across, finally simplify.