Question

A cuboid is formed of 3 edges measuring 3, 4 and 5 cm. It is sliced into two identical solids by a plane through a diagonal of the smallest of the faces. The surface area of the sliced section is 

(a) 12 cm² 

(b) 15 cm² 

(c) 20 cm² 

(d) 25 cm² 

Answer 1

(d) 25 cm²

Area of sliced section DBFH = DB × BF 

DB² = AD² + AB² = 4² + 3² = 16 + 9 = 25 

⇒ DB = 5

∴ Required area = (5 × 5) cm² = 25 cm².