Examples with solutions for All Operations in Fractions: Worded problems

Exercise #1

Dana buys a large packet of crisps.

On the first day, she eats 12 \frac{1}{2} of the packet.

The second day, she eats 13 \frac{1}{3} of the packet.

On the third day, she eats 14 \frac{1}{4} of the packet.

How much of the packet does she eat over the three days?

Step-by-Step Solution

To solve this problem, we need to add the fractions of the packet that Dana eats over the three days.

Let's outline our steps:

  • Step 1: Find the common denominator for the fractions 12\frac{1}{2}, 13\frac{1}{3}, and 14\frac{1}{4}.
  • Step 2: Convert each fraction to an equivalent fraction with the common denominator.
  • Step 3: Add the fractions together.

Step 1: Determine the least common denominator (LCD).
The denominators are 2, 3, and 4. The least common multiple (LCM) of these numbers is 12. Hence, the common denominator is 12.

Step 2: Convert each fraction:
- 12=1×62×6=612\frac{1}{2} = \frac{1 \times 6}{2 \times 6} = \frac{6}{12}
- 13=1×43×4=412\frac{1}{3} = \frac{1 \times 4}{3 \times 4} = \frac{4}{12}
- 14=1×34×3=312\frac{1}{4} = \frac{1 \times 3}{4 \times 3} = \frac{3}{12}

Step 3: Add the fractions:
612+412+312=6+4+312=1312\frac{6}{12} + \frac{4}{12} + \frac{3}{12} = \frac{6+4+3}{12} = \frac{13}{12}

The amount Dana eats over the three days is 1312\frac{13}{12} of the packet.

This means that Dana ate more than a whole packet (since 1312\frac{13}{12} is more than 1).

Therefore, the solution to the problem is 1312\frac{13}{12}.

Answer

1312 \frac{13}{12}

Exercise #2

A mother spends 16 \frac{1}{6} of an hour preparing a salad and 23 \frac{2}{3} of an hour cooking french fries.

How much time does she spend preparing food (as a fraction of an hour)?

Step-by-Step Solution

The mother spends time preparing both salad and french fries. We need to sum up these two times:

Given the times:

  • Salad: 16 \frac{1}{6} hour
  • French fries: 23 \frac{2}{3} hour

To add these fractions, we need a common denominator. The denominators are 6 and 3. The least common multiple of 6 and 3 is 6.

Convert 23 \frac{2}{3} to a fraction with a denominator of 6:

23=2×23×2=46 \frac{2}{3} = \frac{2 \times 2}{3 \times 2} = \frac{4}{6}

Now, add the fractions:

16+46=1+46=56 \frac{1}{6} + \frac{4}{6} = \frac{1 + 4}{6} = \frac{5}{6}

Therefore, the total time the mother spends preparing food is 56 \frac{5}{6} of an hour.

Answer

56 \frac{5}{6}

Exercise #3

Marcos takes 27 \frac{2}{7} of the money out of his piggy bank.

How much more does he need to take out so that only half remains?

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Determine how much of the original amount remains after taking out 27\frac{2}{7}.
  • Step 2: Calculate how much more needs to be removed so that only half of the original amount remains in the piggy bank.
  • Step 3: Perform the necessary calculations to find the additional amount required to be taken out.

Now, let's work through each step:

Step 1: Initially, Marcos takes out 27\frac{2}{7} of his money. Therefore, the remaining money is:

127=7727=571 - \frac{2}{7} = \frac{7}{7} - \frac{2}{7} = \frac{5}{7}

Step 2: We want only half of the initial amount, or 12\frac{1}{2}, to remain. Let xx be the additional fraction of money taken out.

Equation: 57x=12\frac{5}{7} - x = \frac{1}{2}

Step 3: Solve for xx. First, get a common denominator for the fractions on the right.

57x=12\frac{5}{7} - x = \frac{1}{2}

Find a common denominator (here, 14 works):

5×27×2x=1×72×7\frac{5 \times 2}{7 \times 2} - x = \frac{1 \times 7}{2 \times 7}

1014x=714\frac{10}{14} - x = \frac{7}{14}

Subtracting 714\frac{7}{14} from both sides gives us:

1014714=x\frac{10}{14} - \frac{7}{14} = x

Hence, x=314x = \frac{3}{14}.

Therefore, the solution to the problem is that Marcos needs to take out an additional amount of 314\frac{3}{14} of his money.

Answer

314 \frac{3}{14}

Exercise #4

Daniel buys a roll of paper, uses25 \frac{2}{5} of the paper to wrap a book and 34 \frac{3}{4} to wrap a notebook.

How much of the paper roll does Daniel use?

Step-by-Step Solution

To solve this problem, we will add the fractions representing the amount of paper Daniel uses:

  • Step 1: Identify the fractions of the paper roll used.
    Daniel uses 25 \frac{2}{5} of the roll for the book and 34 \frac{3}{4} for the notebook.
  • Step 2: Find a common denominator.
    The denominators are 5 and 4. The least common multiple of 5 and 4 is 20. Hence, the common denominator will be 20.
  • Step 3: Convert each fraction to have this common denominator.
    • For 25 \frac{2}{5} , convert it to 25×44=820 \frac{2}{5} \times \frac{4}{4} = \frac{8}{20} .
    • For 34 \frac{3}{4} , convert it to 34×55=1520 \frac{3}{4} \times \frac{5}{5} = \frac{15}{20} .
  • Step 4: Add the two fractions.
    Add 820+1520=2320 \frac{8}{20} + \frac{15}{20} = \frac{23}{20} .
  • Step 5: Interpret the result.
    The result 2320 \frac{23}{20} implies that Daniel used more than one whole roll, specifically 2320 \frac{23}{20} of the paper roll in total.

Therefore, the solution to the problem is 2320 \frac{23}{20} .

Answer

2320 \frac{23}{20}

Exercise #5

Ned spends 18 \frac{1}{8} of an hour doing his language homework and 68 \frac{6}{8} of an hour doing his science homework.

How long does Ned spend doing his homework (as a fraction of an hour)?

Step-by-Step Solution

To solve the problem of determining how long Ned spends doing his homework, we need to add the times he spent on language and science homework.

Given:
- Language homework: 18 \frac{1}{8} of an hour
- Science homework: 68 \frac{6}{8} of an hour

Since both times have the same denominator, adding them is straightforward:

18+68=1+68=78 \frac{1}{8} + \frac{6}{8} = \frac{1+6}{8} = \frac{7}{8}

Therefore, Ned spends 78 \frac{7}{8} of an hour doing his homework.

Answer

78 \frac{7}{8}

Exercise #6

Sarah receives a school assignment.

In the first hour, she does 28 \frac{2}{8} of the work, while in the second hour she completes 14 \frac{1}{4} of the work.


How much of the assignment does Sarah do in total?

Step-by-Step Solution

To solve this problem, we will add the fractions of the work Sarah completed in the first and second hours:

  • Step 1: Identify the fractions: Sarah completed 28 \frac{2}{8} of the work in the first hour and 14 \frac{1}{4} of the work in the second hour.
  • Step 2: Convert the fractions to have the same denominator. The denominators are 8 and 4, respectively. The least common denominator (LCD) of 8 and 4 is 8.
  • Step 3: Convert 14 \frac{1}{4} to a fraction with a denominator of 8. Since 14=28 \frac{1}{4} = \frac{2}{8} , we convert it as follows: 14=1×24×2=28 \frac{1}{4} = \frac{1 \times 2}{4 \times 2} = \frac{2}{8}
  • Step 4: Add the fractions with the common denominator: 28+28=2+28=48 \frac{2}{8} + \frac{2}{8} = \frac{2 + 2}{8} = \frac{4}{8}
  • Step 5: Simplify the resulting fraction. Divide the numerator and the denominator by their greatest common divisor, which is 4: 48=4÷48÷4=12 \frac{4}{8} = \frac{4 \div 4}{8 \div 4} = \frac{1}{2}

Therefore, Sarah completed 12 \frac{1}{2} of the assignment in total.

Answer

12 \frac{1}{2}