A rectangular tank measuring 5 m × 4.5 m × 2.1 m is dug in the centre of the field measuring 13.5 m × 2.5. The earth dug out is spread evenly over the remaining portion of a field. How much is the level of the field raised ?  Choose the correct choice from the following:
A) 4.0 m  B) 4.1 m  C) 4.2 m  D) 4.3 m  E) None of these
Area of the field = 13.5 × 2.5 = 33.75 m2   Area covered by the rectangular tank   = 5 × 4.5 = 22.50 m2   Area of the field on which the earth dug out is to be spread = 33.75 – 22.50 = 11.25 m2   Let the required height be h.   Then, 11.25 × h = 5 × 4.5 × 2.1   or h = 4.2 m   Answer 4.2 m
<result>C</result>
A rectangular tank measuring 5 m × 4.5 m × 2.1 m is dug in the centre of the field measuring 13.5 m × 2.5. The earth dug out is spread evenly over the remaining portion of a field. How much is the level of the field raised ?