6 men can complete the electric fitting in a building in 7 days. How many days will it take 21 men to do the job? ​

Number of days required by 6 men to complete the work = 7

Number of days required by 1 man to complete the work = 7 × 6

Number of days required by 21 men to complete the work = 42/21 = 2

Hence, 2 days is required by 21 men to complete the work