# #27. Question of the Week

**How to solve problem sums involving Common Identity?**

Common Identity Concept is first introduced and tested extensively in Primary 3. Below is an example of a Common Identity Concept question.

A kettle and 3 bottles can hold 46 L of water.

A kettle and 6 bottles can hold 52 L of water.

How much water can a kettle hold?

Solution.

Kettle + 3 bottles → 46 L

Kettle + 6 bottles → 52 L

3 bottles → 52 L – 46 L= 6 L

Kettle → 46 L – 6 L = 40 L

**Answer: 40 L**

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