A hall 36m long and 15m broad is to be paved with stones, each measuring 4dm by 5 dm. The number of stones required is: Choose the correct choice from the following:  A) 180  B) 2700  C) 18  D) 18000  E) 1.8

Rationale: "area of the hall = 3600 * 1500 area of each stone = ( 40 * 50 ) therefore , number of stones = ( 3600 * 1500 / 40 * 50 ) = 2700 answer : b"
Answer: B