Question

The table below shows four problems using decimals.

Problem Number
Problem
1
How many grams are in 2.3 kilograms? Recall that there are 1000 grams in a kilogram.
2
How many 85-cent nutrition bars can Mary buy for $20.00?
3
How many quarts does Mike have to buy for a recipe that calls for 13.7 cups? Recall that there are 4 cups in a quart.
4
How many days will a trip take if it takes 152.45 hours? Recall that there are 24 hours in a day.

Which problem would be solved using multiplication, and what is the solution to the problem?
Problem 1 requires multiplication. There are 2300 grams in 2.3 kilograms.
Problem 2 requires multiplication. Mary can buy 23 nutrition bars.
Problem 3 requires multiplication. Mike has to buy 54.8 quarts for the recipe.
Problem 4 requires multiplication. The trip will take 3658.8 days.

Answer 1

Let's analyze each problem to determine whether they require multiplication (or division where appropriate) and to identify the correct solutions.

1. **Problem 1: How many grams are in 2.3 kilograms?**
- This problem does require multiplication, specifically, you multiply the kilograms by the number of grams in a kilogram:
\[
2.3 \text{ kg} \times 1000 \text{ g/kg} = 2300 \text{ g}
\]
- Correct solution: There are **2300 grams** in 2.3 kilograms.

2. **Problem 2: How many 85-cent nutrition bars can Mary buy for $20.00?**
- This requires division, not multiplication, to determine how many bars she can purchase:
\[
\frac{20.00}{0.85} \approx 23.53
\]
- Since Mary can only buy whole bars, she can buy **23 nutrition bars**.

3. **Problem 3: How many quarts does Mike have to buy for a recipe that calls for 13.7 cups?**
- This requires division, as you divide the number of cups by the number of cups in a quart:
\[
\frac{13.7 \text{ cups}}{4 \text{ cups/quart}} = 3.425 \text{ quarts}
\]
- The correct interpretation would be that Mike needs about **3.43 quarts** (or 3 quarts and a little more).

4. **Problem 4: How many days will a trip take if it takes 152.45 hours?**
- This also requires division:
\[
\frac{152.45 \text{ hours}}{24 \text{ hours/day}} \approx 6.352 \text{ days}
\]
- Thus, the trip will take about **6.35 days**.

### Summary of Problems:
- **Problem 1:** Requires multiplication. **Correct answer: 2300 grams.**
- **Problem 2:** Requires division. **Correct answer: 23 bars.**
- **Problem 3:** Requires division. **Correct answer: approximately 3.43 quarts.**
- **Problem 4:** Requires division. **Correct answer: approximately 6.35 days.**

The only problem that was correctly identified as multiplication is Problem 1. The solutions for Problems 2, 3, and 4 were mistakenly described as requiring multiplication. The correct calculations for Problems 2, 3, and 4 involve division.