Before and After problem sums in PSLE math often involve identifying a variable that remains constant before and after a change occurs. This method relies on understanding how certain quantities are affected by adjustments and using this knowledge to find the solution. Let’s delve into an example to illustrate this concept.

**Example:**

**Question:**

1/5 of the students at Ace Scorers tuition centre were girls and the rest were boys. When 8 girls left the centre, the fraction of girls decreased to 1/7 of the total number of students at the centre. How many students were at the tuition centre at first?

**Solution:** To solve this problem, we need to identify the variable that remains constant before and after the change. In this case, the number of boys remains unchanged.

**Step 1: Identify the Unchanged Variable** Variable that does not change: Number of Boys

**Step 2: Set Up the Equation** Before the change:

**Step 3: Find the Total**:

**Answer:** At first, there were 120 students at the tuition centre.

By understanding the concept of variables and applying the Before and After method, students can effectively solve PSLE math problem sums and arrive at the correct answers with confidence.

This article provides valuable insights and strategies for mastering this essential problem-solving technique in PSLE math.

Check out the details hereĀ Intro to 7 different types of PSLE Math problem sums – YouTube