Question

In a rhombus of side 10cm, one of the diagonals is 12cm long. The length of the second diagonal is 

(a) 20cm (b) 18cm (c) 16cm (d) 22cm

Answer 1

(c) 16 cm

Let ABCD be the rhombus with diagonals AC and BD intersecting each other at O. 

Also, diagonals of a rhombus bisect each other at right angles.

If AC = 12 cm, AO = 6 cm 

Applying Pythagoras theorem in right-angled triangle AOB. We get:

Hence, the length of the second diagonal BD is 16 cm.