How would you solve this aptitude test for army?
In one hour, a machine can dig a hole with diameter 10 cm through a 1.75 m depth of consistently hard rock. The machine is required to dig to a total depth of 112 m. If the machine is used for a total of 7 hours per day, how many days will it take for the machine to complete the task?
Answer is B according to the book but how did they get the answer? I keep getting A