Dividing Fractions
This is the rule you use when dividing fractions.
What is multiply by the reciprocal (keep-change-flip)?
A student solves
3/4 divided by a 1/2
by multiplying 3/4 x 1/2
What mistake did the student make?
What is they forgot to flip the second fraction (use the reciprocal)?
A ribbon is 2 yards long. Each piece needs 1/2 yard.
How many pieces can be cut?
What is 4 pieces?
A student solved:
4.5 + 2.35 = 6.80
What is the correct answer?
What is 6.85?
A student types into the calculator:
8 + 4 × 2
The student expects the answer 24.
Who is correct?
What is the calculator (16)?
Solve:
3/4 divided by a 1/2
What is 1 1/2
A student solves
1 1/2 divided by 3/4
by writing 1/2 divided by 3/4
What mistake did they make?
What is they ignored the whole number instead of converting the mixed number to an improper fraction?
A baker uses 2/3 cup of sugar for each batch of cookies.
If she has 4 cups of sugar, how many batches can she make?
What is 6 batches?
A student solved:
7.2 − 3.18 = 4.02
What is the correct answer?
What is 4.02?
A student types:
20 − 5 × 3
The student expects the answer 45.
What answer will the calculator show?
What is 5?
A recipe uses 3/4 cup of sugar per batch. You have 2 cups of sugar.
How many batches can you make?
What is 2 2/3 batches?
A student solves
2/3 divided by 4/5
by flipping both fractions.
What mistake did they make?
What is they should only flip the second fraction (the divisor)?
A rope is 3 meters long. Each jump rope needs 3/4 meter.
How many jump ropes can be made?
What is 4 jump ropes?
A student solved:
3.6 × 4 = 14.4
The student says the answer is 144.
What mistake did the student make?
What is they forgot the decimal point?
A student wants to solve:
(8 + 4) × 2
But types:
8 + 4 × 2
What answer will the calculator give?
What is 16 instead of 24?
1 1/2 divided by 3/4
2
A student says
1/2 divided by 1/4 = 1/8.
What mistake did they make?
What is they multiplied instead of multiplying by the reciprocal?
A student drinks 3/4 liter of water each day.
How much water does the student drink in 6 days?
What is 4 1/2 liters?
A student solved:
8.4 ÷ 2 = 4.2
Another student says the answer should be 42.
Who is correct?
What is the first student (4.2 is correct)?
A student wants to divide 9 by 3 + 3.
They type:
9 ÷ 3 + 3
What answer will the calculator give?
What is 6?
A ribbon is 3 1/2 yards long. Each piece needs 5/8 yard.
How many pieces can be cut?
What is 5 3/5 pieces?
A student solves this problem:
A 3-cup container is filled with servings of 3/4 cup each.
They multiply 3 x 3/4.
What mistake did they make?
What is they should divide because the problem asks how many groups fit into the total?
Each small pizza uses 2/3 pound of cheese.
If a restaurant makes 9 pizzas, how much cheese is needed?
What is 6 pounds?
A student solved:
2.5 + 0.75 = 0.100
What is the correct answer?
What is 3.25?
A student wants to find:
(15 − 5) × (6 + 2)
But types:
15 − 5 × 6 + 2
What answer will the calculator give?
What is −13?