BrainBashers - Random Puzzles

Puzzle 13

Starting with SOFT, change one letter at a time until you have the word LENS.

Each change leaves the other letters in their original places and must result in a proper word.

What is the minimum number of steps required to achieve this change?
SOFT
....
....
....
LENS

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Puzzle 14

What is the only number not found in the Roman numerals system?

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Puzzle 15

Which is larger?

3 raised to the 5^th power 5 raised to the 3^rd power

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Puzzle 16

How much soil is there …

… in a circular hole 2 metres deep and 1 metre across?

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