Quick diagnosis
Try all three. Explain with words, a sketch, or objects.
d1. One half of a sandwich is shared equally by 3 people. Does each person receive more or less than half a sandwich?
Answer: Less than half; each receives 1/6 of the original whole sandwich.
Look for:
- Predicts less than 1/2.
- Names 1/6 of the original sandwich.
Teacher response: Likely difficulty: Interpreting division as counting how many halves fit in three sandwiches. Response: Keep only one half available and separate it into three equal shares.
d2. A student writes 1/4 ÷ 2 = 2/4. Explain why this cannot describe equal sharing.
Answer: Sharing the available fourth between two people gives each 1/8, not 2/4; two fourths exceed the entire available amount.
Look for:
- Rejects 2/4 by checking the available amount.
- Finds 1/8.
Teacher response: Likely difficulty: Multiplying the unit fraction by the number of recipients. Response: Check whether two copies of the claimed share fit into the original fourth.
d3. One third of a strip is shared among 4 people. A student calls each share 1/4. Of which whole is that true, and what fraction of the original strip is each share?
Answer: Each share is 1/4 of the available third, but 1/12 of the original whole strip.
Look for:
- Distinguishes the two reference amounts.
- Names 1/12 of the original strip.
Teacher response: Likely difficulty: Changing the reference whole from the original strip to the available amount. Response: Keep two labeled outlines: the full strip and its available third.
Practice
For a short session, choose three tasks. Use the others for a second try or follow-up.
p1. Share 1/2 liter of juice equally into 4 cups. How much goes in each cup?
Answer: 1/8 liter.
Look for:
- Finds 1/8 liter per cup.
- Checks four portions make 1/2 liter.
Teacher response: Likely difficulty: Treating four cups as four whole liters to divide by a half. Response: Draw only the half liter available and split it into four equal portions.
p2. Find 1/6 ÷ 3 and explain how many equal shares of that size fit in the original whole.
Answer: 1/18; eighteen such shares fit in one whole.
Look for:
- Finds 1/18.
- Connects 6 × 3 to pieces per whole.
Teacher response: Likely difficulty: Using 6 + 3 for the new denominator. Response: Split each of six sixths into three equal pieces.
p3. A student shares 1/4 of a pie among 3 people and gives each 1/12 of the pie. Verify the answer without repeating a division rule.
Answer: Three shares total 3 × 1/12 = 3/12 = 1/4, so the answer is correct.
Look for:
- Uses multiplication or recombination.
- Shows the total is exactly the available fourth.
Teacher response: Likely difficulty: Accepting a fraction without checking it reconstructs the starting amount. Response: Join three twelfth-sized pieces and compare them with the available fourth.
p4. Which gives a larger share: 1/3 ÷ 2 or 1/3 ÷ 5? Explain before calculating.
Answer: 1/3 ÷ 2 is larger. The same third shared by fewer people gives larger shares: 1/6 versus 1/15.
Look for:
- Chooses the two-person share.
- Explains 1/6 > 1/15 using equal available amounts.
Teacher response: Likely difficulty: Thinking a larger divisor gives a larger share. Response: Keep the available third fixed and compare two-way with five-way partitions.
p5. One eighth of a cake is given to one person. Write the division and result.
Answer: 1/8 ÷ 1 = 1/8.
Look for:
- Finds 1/8.
- Explains that dividing by 1 keeps the amount.
Teacher response: Likely difficulty: Assuming every division must make an amount strictly smaller. Response: Ask whether sharing with one recipient splits the available piece at all.
p6. Make a story for 1/5 ÷ 3. Include the available amount, number of equal shares, and amount in one share.
Answer: Example: 1/5 liter is poured equally into 3 cups, with 1/15 liter in each.
Look for:
- Matches a unit-fraction available amount and 3 recipients.
- Finds 1/15 in the same original unit; equivalent stories count.
Teacher response: Likely difficulty: Writing an integer-divided-by-unit-fraction story for the reversed operation. Response: Start the story with exactly one fifth available, not five or three whole units.