**Find the length**

*AC. [Diagram not to scale]*

__Suluhu__

**We will use the PYTHAGORAS theorem [ a**

^{2}+ b^{2}= c^{2 }]

**a**

^{2}+ b^{2}= c^{2 }

^{}**AB**

^{2}+ BC^{2}= AC^{2 }

**3**

^{2}+ 4^{2}= AC^{2 }

**9 + 16 = AC**

^{2 }

**25 = AC**

^{2}[Here, we find the square root of 25]

**5 = AC**

__Hence AC = 5mm__