TWO CHIMNEYS 18 M AND 13M HIGH STAND UPRIGHT ON A GROUND .IF THEIR FEET IS 12M APART , THEN THE DISTANCE BETWEEN THEIR TOPS IS? 

 It is a question of pythagoras theorem

Distance beween two chimneys = 12 m ( base)

Difference in height = 18 - 13 = 5m ( perpendicular)

Now distance between their tops= ? ( hypotenuse)

?² = 5² + 12²

?² = 25 + 144

?² = 169

? = square root of 169

? = 13 M

Ans: 13 m