This question tests the concept of work rate and how much work is completed in a given time period.

A completes the entire work in 20 days, so the work rate is 1 part per day.

Multiply the daily work rate by the number of days.

Reduce the fraction to its simplest form by dividing both numerator and denominator by 5.

A will complete 1/4 of the work in 5 days.

This question asks us to find B's daily work rate when the total job can be completed in 15 days.

Work rate is the fraction of total work completed per day.

Since B completes the entire job, the total work equals 1.

B completes the job in 15 days, so divide the work by the number of days.

B's work rate is 1/15 of the job per day, which means B completes one-fifteenth of the job each day for 15 days to finish it completely.

This question tests the concept of inverse proportionality between the number of workers and the time required to complete a fixed task.

Work is constant regardless of the number of workers, so we multiply workers by days.

With 10 workers, the same 40 worker-days of work must be completed.

Divide total work by the number of workers to find days required.

When 10 workers work together, they will build the same wall in 4 days.

60% work is done in 9 days.

Rate = 0.6/9 = 1/15 per day.

Total days = 1/(1/15) = 15 days

Total distance = 240 + 360 = 600m. Time = 30 seconds. Speed = 600/30 = 20 m/s = 20 × 3.6 = 72 km/h

Profit = 25% of 800 = 200. Selling Price = 800 + 200 = ₹1000

Upstream speed = 15-3 = 12 km/h. Downstream speed = 15+3 = 18 km/h. Time upstream = 36/12 = 3 hours. Time downstream = 36/18 = 2 hours. Total = 5 hours

SI = (P × R × T)/100 = (5000 × 8 × 2.5)/100 = 100000/100 = ₹1000

A = P(1 + r/100)^n = 10000(1.1)^2 = 10000 × 1.21 = 12100. CI = 12100 - 10000 = ₹2100

Fill rate = 1/20, Drain rate = 1/30. Net rate = 1/20 - 1/30 = 3/60 - 2/60 = 1/60. Time = 60 minutes