Fraction Classroom · 2.2.0 · Teacher answers & responses

Why can dividing a decimal give a larger number?

Count how many small measured groups fit in an amount, and name the unit of the quotient.

Four equal jumps of 0.2 reach 0.8. Each interval represents one piece.00.20.40.60.80.8
Four equal jumps of 0.2 reach 0.8. Each interval represents one piece.

Discuss the opening question

start. How many 0.2-metre pieces fit in 0.8 metres of ribbon?

Answer: Four pieces. Eight tenths contains four groups of two tenths, so 0.8 ÷ 0.2 = 4.

Teacher response: Listen for this idea: Division must produce a number smaller than the starting number. Follow up: This quotient counts groups. The dividend is a length, while the quotient is a number of pieces. A small group size can fit many times.

Work through the explanation

example. How many 0.2-metre pieces fit in 0.8 metres of ribbon?

  1. Name both units: the total is 0.8 metres, and each piece is 0.2 metres. Assume exact cuts with no loss for this mathematics task.
  2. Rename both lengths in tenths of a metre. Ask how many groups of two tenths fit in eight tenths.
  3. Count four groups and record a quotient of 4 pieces. Do not label it 4 metres.
  4. Check with multiplication: four pieces × 0.2 metres per piece = 0.8 metres. The product recovers the original length.

Worked example: Four pieces. Eight tenths contains four groups of two tenths, so 0.8 ÷ 0.2 = 4.

Practise, then check independently

Use p1–p3 for practice. Try e1 without help. Show how your place-value units or model support the result.

p1. How many 0.3-metre pieces fit in 0.9 metres? Enter the piece count.

Answer: 3

Teacher response: Nine tenths contains three groups of three tenths.

p2. How many 0.25-litre servings fit in 1 litre? Enter the serving count.

Answer: 4

Teacher response: Four quarter-litre servings make one litre.

p3. Calculate 0.6 ÷ 0.1.

Answer: 6

Teacher response: Six groups of one tenth fit in six tenths.

e1. How many 0.2-metre pieces fit in 1.4 metres? Enter the piece count.

Answer: 7

Teacher response: Fourteen tenths divided into groups of two tenths makes seven groups.

Explain a new situation

transfer. Compare the questions 0.8 ÷ 4 and 0.8 ÷ 0.2. What does each answer measure?

Answer: 0.8 ÷ 4 shares 0.8 into four equal groups, each of size 0.2. In the ribbon context, that is metres per piece. 0.8 ÷ 0.2 asks for the count of 0.2-metre pieces: 4.

Choose the next teaching move

next. If the learner confuses size and count, draw the groups and label both quantities before calculating.

Teaching notes