Answer: 1) 15 hrs, 2) 3 days, 3) 6 days, 4) 16 beads/min
Explanation:
1) if the train travels 200km in 5 hrs, it travels 40km/hr, (200/5, since S=D/T). If the train is traveling 40km every hour, it will take it 15 hrs, (600/40) to travel 600km
2) if 2 men can weed a compound in 6 days, 4 men can do it in half the time, (since the workforce is double, the time taken is divided by 2). So it will take 4 people 3 days to weed the compound.
3) If 3 men can mow a lawn in 4 days, then 3 men can mow 1/4 of the lawn in 1 day. 1 man can mow 1/12 of the lawn in 1 day. So 2 men can mow 1/6 of the lawn in 1 day. .: it will take 6 days for 2 men to mow the same lawn.
4. If Lia can string 48 beads in 3 minutes, she can do 16 beads in 1 minute. 1 is 1/3 of 3, and 16 is 1/3 of 48, so the logic checks out.