Examples with solutions for Multiplication of Integers by a Fraction and a Mixed number: Worded problems

Exercise #1

Chris runs 2 km in 412 4\frac{1}{2} minutes.

How many minutes does he run on average per km?

Video Solution

Step-by-Step Solution

To solve this problem, we need to calculate the average time Chris spends running per kilometer. We are given that Chris runs 2 km in 412 4\frac{1}{2} minutes.

First, let's convert the mixed fraction 412 4\frac{1}{2} into an improper fraction. The whole number 4 and the fraction 12 \frac{1}{2} combine as follows:

412=4×2+12=92 4\frac{1}{2} = \frac{4 \times 2 + 1}{2} = \frac{9}{2}

This means that the total time taken is 92 \frac{9}{2} minutes.

Next, we find the average time Chris runs per kilometer by dividing the total time by the distance:

Average time per km=Total timeTotal distance in km=922 \text{Average time per km} = \frac{\text{Total time}}{\text{Total distance in km}} = \frac{\frac{9}{2}}{2}

To divide by a fraction, we multiply by its reciprocal:

922=92×12=94 \frac{\frac{9}{2}}{2} = \frac{9}{2} \times \frac{1}{2} = \frac{9}{4}

The fraction 94 \frac{9}{4} can be converted back into a mixed number:

94=214 \frac{9}{4} = 2\frac{1}{4}

Therefore, the average time Chris runs per kilometer is 214 2\frac{1}{4} minutes.

Answer

214 2\frac{1}{4}

Exercise #2

A mother has \( 2\frac{1}{2} and wants to distribute it equally among her 2 children.

How much in dollars will each child receive?

Video Solution

Step-by-Step Solution

To solve this problem, we will follow these steps:

  • Step 1: Convert the mixed number 2122\frac{1}{2} to an improper fraction.
  • Step 2: Divide the improper fraction by 2.
  • Step 3: Simplify the resulting fraction if necessary.

Now, let's work through each step:
Step 1: Convert the mixed number 2122\frac{1}{2} to an improper fraction. This is done by multiplying the whole number 2 by the denominator 2 and adding the numerator 1. Hence, 212=2×2+12=522\frac{1}{2} = \frac{2 \times 2 + 1}{2} = \frac{5}{2}.
Step 2: Divide 52\frac{5}{2} by 2. Dividing by 2 is equivalent to multiplying by 12\frac{1}{2}. Therefore, 52÷2=52×12=54\frac{5}{2} \div 2 = \frac{5}{2} \times \frac{1}{2} = \frac{5}{4}.
Step 3: The fraction 54\frac{5}{4} is already in its simplest form, but it can also be expressed as a mixed number: 1141\frac{1}{4}.

Therefore, each child will receive 1141\frac{1}{4} dollars.

Answer

114 1\frac{1}{4}

Exercise #3

Ruth divided an apple pie into 4 equal parts and her husband ate a piece.

Ruth wants to divide the remaining pie into equal parts for her 3 children.

How much will each child receive?

Step-by-Step Solution

To solve this problem, we need to determine how much of the pie each child will receive after Ruth's husband has eaten one piece.

Let's break it down step by step:

  • Step 1: Determine the remaining pie.
    • The pie was cut into 4 equal pieces, and 1 piece was eaten. So, the fraction of the pie remaining is:
    • 4414=34 \frac{4}{4} - \frac{1}{4} = \frac{3}{4}
  • Step 2: Divide the remaining pie among the 3 children.
    • To divide 34 \frac{3}{4} equally among 3 children, we perform:
    • 34÷3=34×13 \frac{3}{4} \div 3 = \frac{3}{4} \times \frac{1}{3}
    • When multiplying fractions, multiply the numerators and the denominators:
    • 3×14×3=312=14 \frac{3 \times 1}{4 \times 3} = \frac{3}{12} = \frac{1}{4}

Thus, each child will receive 14 \frac{1}{4} of the pie.

Therefore, the solution to the problem is 14 \frac{1}{4} , which corresponds to choice 2.

Answer

14 \frac{1}{4}

Exercise #4

Four children go to a restaurant to eat pizza.

Each child eats half a pizza.

How many pizzas do the children eat in total?

Video Solution

Step-by-Step Solution

To solve this problem, let's proceed step by step:

  • Step 1: Identify the given information:
    We know that there are 4 children and each child eats 12 \frac{1}{2} pizza.
  • Step 2: Apply the formula:
    We use the formula: Total pizza consumed = Number of children × Amount of pizza per child. Here, this is 4×12 4 \times \frac{1}{2} .
  • Step 3: Perform the calculation:
    Calculate 4×12=42=2 4 \times \frac{1}{2} = \frac{4}{2} = 2 .

Conclusion:
The total number of pizzas consumed by the children is 2 2 .

Answer

2 2

Exercise #5

Joel ran 112 1\frac{1}{2} km in 3 minutes.

How many kilometers did Joel travel on average each minute?

Video Solution

Step-by-Step Solution

To find out how many kilometers Joel ran on average each minute, we begin with these steps:

  • Step 1: Convert the mixed number 112 1\frac{1}{2} km into an improper fraction. The mixed number represents 1 full unit plus half a unit, which is calculated as:

112=1+12=32 1\frac{1}{2} = 1 + \frac{1}{2} = \frac{3}{2} km

  • Step 2: Use the average formula to calculate the distance per minute:

Average distance per minute=32 km3 minutes \text{Average distance per minute} = \frac{\frac{3}{2} \text{ km}}{3 \text{ minutes}}

Simplifying this expression involves dividing fractions:

323=32×13=32×3=36=12 \frac{\frac{3}{2}}{3} = \frac{3}{2} \times \frac{1}{3} = \frac{3}{2 \times 3} = \frac{3}{6} = \frac{1}{2} km per minute

Therefore, Joel traveled, on average, 12 \frac{1}{2} km per minute. This matches the provided correct answer, confirming choice 4 is correct.

Answer

12 \frac{1}{2}

Exercise #6

Daniel swims lengths of 2212 22\frac{1}{2} m.


He completes a length in 7 seconds.

How many meters does he swim per second?

Video Solution

Step-by-Step Solution

Let's solve the problem step-by-step:

Step 1: Convert the mixed fraction to an improper fraction.
The mixed number 2212 22\frac{1}{2} can be expressed in terms of improper fraction as follows:
First, convert 2212 22\frac{1}{2} to an improper fraction:
2212=2×22+12=452 22\frac{1}{2} = \frac{2 \times 22 + 1}{2} = \frac{45}{2} .

Step 2: Use the speed formula.
We know that speed = distance / time. Here, the distance is 452 \frac{45}{2} meters and the time is 7 seconds.
To find meters per second, we calculate:
452÷7=452×17=4514 \frac{45}{2} \div 7 = \frac{45}{2} \times \frac{1}{7} = \frac{45}{14} .

Step 3: Simplify the fraction.
The fraction 4514 \frac{45}{14} can be simplified. It converts to mixed number as follows:
First, divide 45 by 14 which gives a quotient of 3 and a remainder of 3.
Therefore, 4514=3314 \frac{45}{14} = 3\frac{3}{14} .

Therefore, Daniel swims 3314 3\frac{3}{14} meters per second.

Answer

3314 3\frac{3}{14}