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CBSE Class 4 · Mathematics

The Transport Museum

Official NCERT chapter from Math-Mela (book code demm1). ExamMaster notes are original teaching at CBSE Class 4 depth.

This lesson follows the official chapter “The Transport Museum” in Math-Mela. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.

  • CBSE Class 4
  • Easy level
  • 8 concepts

1A mystery matrix is a grid of facts you complete

Rows and columns hold numbers that follow one rule. A blank cell is a fact you can finish from that rule.

A pretty vehicle drawing is not a cell.

Figure. A mystery matrix is a fact grid you finish. Each row keeps one rule: wheels each times how many vehicles equals the total. Cycle 2 × 6 = 12 and car 4 × 3 = 12, so the empty auto cell is 3 × 4 = 12 — not a new kind of multiply.

How it works

  1. See the gridRows and columns.
  2. Name the ruleTimes, or wheels…
  3. Fill a blank from the ruleOne missing fact.

2A 1-digit factor times a partner rebuilds a product

If a cell is 7 \times 6, the product is 42. One factor times the partner rebuilds the missing product.

Adding the factors is a different story.

Figure. A 1-digit factor rebuilds a two-digit partner by houses. 13 is 10 and 3, so 4 × 13 is 4 tens plus 4 ones: 40 + 12 = 52. The two blocks sit side by side as one product, not two separate sums.

How it works

  1. Find the two factors7 and 6.
  2. Multiply42.
  3. Write the product in the cellThe rebuilt fact.

3Rows and columns keep one rule

A row might be “× 4”. Every cell in that row uses 4 as a factor. Mixing × 4 and + 4 in one row breaks the grid.

Read the header before you fill.

Figure. Rows and columns keep one rule. Each row 2+3+4, 5+1+3, 2+5+2 adds to 9, and each column 2+5+2, 3+1+5, 4+3+2 also adds to 9. If a fill breaks either direction, it is the wrong number.

How it works

  1. Read the row headerThe rule.
  2. Read the column headerThe partner.
  3. Apply that one ruleDo not switch to plus.

4A museum of vehicles can hide equal groups of wheels

3 cars with 4 wheels each are 3 groups of 4. The museum is the story; the groups are the maths.

Counting “3 vehicles” is not the wheel-count.

Figure. A museum of vehicles hides equal groups. Three cars, each with four wheels, is three groups of four — 3 × 4 = 12 wheels. Each square mark is one wheel, not a drawn circle. If one car had a different count, the groups would not be equal and it would not yet be multiplication.

How it works

  1. Name one vehicle’s wheelsThe group size.
  2. Count the vehiclesHow many groups.
  3. MultiplyTotal wheels.

Wheels in a row of autos

5 autos, 3 wheels each. How many wheels?

  • Groups5
  • Size3
  • Product5 × 3 = 15

Pro tip. Equal groups of wheels. Check: 15 ÷ 3 = 5 autos.

5Count wheels as equal groups

Same vehicle kind → same wheels each. Different kinds need different group sizes. Do not mash a bicycle and a car into one ×.

Sort the kind first.

Figure. Count wheels as equal groups. Four cycles with two wheels each is 4 × 2 = 8. Division asks the inverse: 8 wheels shared into groups of 2 makes 4 cycles. The leftover after an unequal share would be a remainder, not an error.

How it works

  1. Sort by kindSame wheel-count.
  2. Write groups × size for that kindOne product.
  3. Add products if several kindsA sum of equal-group stories.

6A missing box is an unknown factor

If 4 × ? = 32, the missing factor is 8. The blank is an unknown factor, not a decoration.

Guessing 10 and not checking is not a fill.

Figure. A missing box is the unknown factor. 4 times what makes 12? The inverse read is 12 ÷ 4 = 3, so the empty factor is 3. Check by putting 3 back: 4 × 3 = 12.

How it works

  1. Write the product you know32.
  2. Write the known factor4.
  3. Divide32 ÷ 4 = 8.

7Check by multiplying back

After ? = 8, check 4 × 8 = 32. The product must rebuild.

A check that uses a new vehicle is not a check.

Figure. Check a share by multiplying back. 12 ÷ 3 = 4 means three groups of 4. Put the groups together again: 3 × 4 = 12, the same total you started with. If the product is not 12, the quotient was wrong.

How it works

  1. Keep the factor you found8.
  2. Multiply by the known factor4 × 8.
  3. Demand the product32, or redo.

8The museum is the story; the grid is the maths

Buses and autos are the picture. Factors, products, and blanks are the grid.

Do not invent a museum-only times.

Figure. The museum is the story; the grid is the maths. Two cars and three bikes are what you see. The grid writes the equal groups: 2 cars × 4 wheels = 8, and 3 bikes × 2 wheels = 6. Change the story and the grid must change with it.

How it works

  1. Keep the settingVehicles.
  2. Compute on the grid rule× or wheels.
  3. Use ordinary multiplicationThe museum is not a new operation.
4 × ? = 32. The missing factor is
  1. 8
  2. 28
  3. 36

32 ÷ 4 = 8. Check: 4 × 8 = 32.

Notes

  • The official chapter title is “The Transport Museum”. Teach the school test for that title, not a contest shortcut.
  • If a step needs a later class, stop. The next official chapter will pick it up.

Formulas

  • Product = factor \times factor.
  • Missing factor = product \div known factor.
  • Wheels = (vehicles of one kind) \times (wheels each).

Recap

Hold these pegs from the official chapter “The Transport Museum”. The wording is ExamMaster’s teaching, not a textbook recap.

A mystery matrix is a grid of facts you complete
Rows and columns hold numbers that follow one rule.
A 1-digit factor times a partner rebuilds a product
If a cell is 7 \times 6, the product is 42.
Rows and columns keep one rule
A row might be “× 4”. Every cell in that row uses 4 as a factor. Mixing × 4 and + 4 in one row breaks the grid.
A museum of vehicles can hide equal groups of wheels
3 cars with 4 wheels each are 3 groups of 4.
Count wheels as equal groups
Same vehicle kind → same wheels each. Different kinds need different group sizes. Do not mash a bicycle and a car into one ×.
A missing box is an unknown factor
If 4 × ? = 32, the missing factor is 8. The blank is an unknown factor, not a decoration.

Practise The Transport Museum

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