✔ A rhombus has four equal sides and opposite angles equal.
Q2. Siti measures a trapezium angle at 110 degrees. What is the adjacent interior angle on the parallel side?
✔ Interior angles on parallel lines sum to 180 degrees.
Q3. Ravi buys a rhombus tile for $2.50. If one angle is 60 degrees, what is the opposite angle?
✔ Opposite angles in a rhombus are always equal.
Show transcript
[Slide 1] Spotting Shapes Around Us
Welcome class. Today we explore angles in rhombus and trapezium shapes found in Tampines. Notice how tiles fit together perfectly without gaps.
[Slide 2] Key Properties to Remember
In a rhombus, opposite angles match exactly. For trapeziums, remember parallel lines make interior angles sum to 180 degrees.
[Slide 3] Mei Ling's Trapezium Sign
Mei Ling sees a sign costing five dollars near the MRT. The top side is parallel to the bottom base. We need to find the missing angle.
[Slide 4] Solving with Bar Model
We draw a bar model representing the straight line angle sum. Subtract seventy-five degrees from the total to find the missing part.
[Slide 5] Avoiding Common Errors
Students often think trapeziums have equal sides like a rhombus. Always check the diagram for parallel line markings before assuming.
[Slide 6] Quick Revision Summary
Remember rhombus diagonals cut angles in half. For trapeziums, use the parallel line rule to find unknowns.