Question 10 of 17intermediate🔧 ApplyNumerical3 marks

A tank on a building has enough water to supply 20 families living there for 6 days. If 10 more families move in there, how long will the water last? What assumptions do you need to make to work out this problem?

Correct Answer

Given: 20 families, water lasts 6 days 10 more families move in

Concept: Inverse proportion Number of families × Days = Constant

Step 1: Calculate total water supply 20×620 \times 6 = 120 family-days

Step 2: Find new number of families 20 + 10 = 30 families

Step 3: Calculate new duration 120 ÷ 30 = 4 days

Answer: The water will last for 4 days.

Assumptions:

  1. Each family consumes the same amount of water per day.
  2. The rate of water consumption remains constant throughout.
Exercise: Figure it Out (Section 4) | Q: 3 | (Page Page 13)
For More Understanding

Explanation

The chapter demonstrates inverse proportion with similar examples. Number of families × Days = Constant (total water supply). Initial: 20×620 \times 6 = 120 family-days. New families = 20 + 10 = 30. Days = 120 ÷ 30 = 4 days.

Solution Steps

  1. Step 1: Calculate total water supply in family-days: 20 families × 6 days = 120 family-days

  2. Step 2: Find new number of families: 20 + 10 = 30 families

  3. Step 3: Calculate new duration: 120 family-days ÷ 30 families = 4 days

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