A bakery recipe calls for 15 tablespoons of flour. How many teaspoons of flour is this?(1 text{ tablespoon} = 3...

1. TRANSLATE the problem information

• Given information:
  • Need to convert 15 tablespoons of flour to teaspoons
  • Conversion factor: \(1\text{ tablespoon} = 3\text{ teaspoons}\)
• What we need to find: Number of teaspoons equivalent to 15 tablespoons

2. INFER the conversion strategy

• Since we're converting from tablespoons (larger unit) to teaspoons (smaller unit), we need to multiply by the conversion factor
• The conversion factor tells us: 1 tablespoon contains 3 teaspoons
• Therefore: 15 tablespoons will contain \(15 \times 3\) teaspoons

3. SIMPLIFY by performing the calculation

• \(15\text{ tablespoons} \times 3\text{ teaspoons/tablespoon} = 45\text{ teaspoons}\)
• The units cancel out properly: tablespoons cancel, leaving teaspoons

Answer: C (45)

Why Students Usually Falter on This Problem

Most Common Error Path:

Weak INFER skill: Students confuse the direction of conversion and divide instead of multiply

Students might think: "Since teaspoons are smaller than tablespoons, I need fewer of them" and incorrectly calculate \(15 \div 3 = 5\).

This may lead them to select Choice A (5).

Second Most Common Error:

Poor TRANSLATE reasoning: Students misunderstand what the problem is asking for

Students might think the problem is asking how many tablespoons equal 15 teaspoons, or they might simply repeat the original measurement without converting.

This may lead them to select Choice B (15).

The Bottom Line:

Unit conversion problems require careful attention to direction - when converting from larger units to smaller units, you multiply (because you need more of the smaller units to equal the same amount).