A laboratory sample has a mass of 485 grams before a reaction. After the reaction, 159 grams of the sample...

1. TRANSLATE the problem information

• Given information:
  • Initial mass before reaction: 485 grams
  • Remaining mass after reaction: 159 grams
  • \(\mathrm{x}\) = mass consumed during reaction
• We need to find: the value of x

2. INFER the mathematical relationship

• The mass consumed must equal the difference between what we started with and what remains
• This gives us the equation: \(\mathrm{x = initial\ mass - remaining\ mass}\)
• Therefore: \(\mathrm{x = 485 - 159}\)

3. SIMPLIFY to find the answer

• Calculate: \(\mathrm{485 - 159 = 326}\)
• Therefore: \(\mathrm{x = 326\ grams}\)

Answer: B (326)

Why Students Usually Falter on This Problem

Most Common Error Path:

Weak TRANSLATE skill: Students misinterpret which quantities to subtract, potentially calculating \(\mathrm{159 - 485}\) instead of \(\mathrm{485 - 159}\), or adding the values instead of subtracting.

This confusion about the problem setup can lead to selecting Choice A (159) if they think the remaining mass is the answer, or getting a negative result that doesn't match any choice, causing them to guess randomly.

The Bottom Line:

This problem tests whether students can correctly translate a real-world conservation scenario into basic arithmetic. The key insight is recognizing that "amount consumed" represents the difference between initial and final quantities.