✔ Substitute 4 for x: 2 times 4 is 8. Add 5 to get 13.
Q2. What is the common mistake in 10 minus 2 times 3?
✔ Students often subtract before multiplying. Multiplication comes first in BODMAS.
Q3. Ravi buys m buns at two dollars each. Which expression shows the cost?
✔ The cost is two dollars multiplied by the number of buns, m.
Show transcript
[Slide 1] Why Learn Algebra?
Hello class! Algebra is like a secret code for money problems. Imagine Ravi buying chicken rice at Tampines Hawker Centre. We use letters to stand for unknown prices.
[Slide 2] The Substitution Rule
To evaluate, simply swap the letter for its value. Always follow the order of operations strictly. This ensures your answer is correct every time.
[Slide 3] Siti's Hawker Bill
Let us look at Siti buying noodles. The expression ten minus two n shows her change. We draw a bar model to visualise the total cost.
[Slide 4] Solving for Three Plates
Since n equals three, we put three in place of n. The bar model shows ten units minus six units. Subtract from ten to find four dollars change.
[Slide 5] Watch Out for Brackets
Many students subtract ten minus two before multiplying. Remember BODMAS rules apply to algebra too. Multiplication must happen before subtraction here.
[Slide 6] Key Takeaways
You have mastered substitution for PSLE maths. Practice with local scenarios like MRT fares. Keep calm and substitute correctly.