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31. If 5 workers can collect 60 kg wheat in 3 days, how many kilograms of wheat will 8 workers collect in 5 days ?

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Solution:
Let the required quantity be x kg.
More workers, More quantity (Direct proportion)
More days, More quantity (Direct proportion)
Workers 5:8Days 3:5}::60:x
 5×3×x=8×5×60x=(8×5×60)(5×3)x=160
32. 50 people consume 350 kg of rice in 30 days. In how many days will 35 people consume 50 kg of rice ?

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Solution:
Let the required number of days be x
Less people, More days (Indirect proportion)
Less quantity, Less days ( Direct proportion)
People 35:50Quantity 350:50}::30:x
 35×350×x=50×50×30x=(50×50×30)(35×350)x=30049x=6649
33. Working 8 hours a day, 12 men can do a work in 30 days. Working 4 hours a day, 18 men can do work in ?

Discuss
Solution:
Let the required number of days be x
Less working hours, More days (Indirect Proportion)
More men, Less days (Indirect Proportion)
Working hours 4:8Men 18:12}::30:x
 4×18×x=8×12×30x=(8×12×30)(4×18)x=40
34. 5 persons can prepare an admission list in 8 days working 7 hours a day. If 2 persons join them so as to complete the work in 4 days, they need to work per day for ?

Discuss
Solution:
Let the number of working hours per day be x
More persons, Less working hours ( Indirect proportion)
Less days, More working hours (Indirect proportion)
Persons 7:5Quantity 4:8}::7:x
 7×4×x=5×8×7x=(5×8×7)(7×4)x=10
35. 4 persons can prepare an admission list in 8 days working 7 hours a day. If 3 persons join them so as to complete the work in 4 days, they need to work per day for ?

Discuss
Solution:
Let the number of working hours per day be x
More persons, Less working hours ( Indirect proportion)
Less days, More working hours (Indirect proportion)
Persons 7:4Quantity 4:8}::7:x
 7×4×x=4×8×7x=(4×8×7)(7×4)x=8
36. 3 pumps , working 8 hours a day, can empty a tank in 2 days. How many hours a day must 4 pumps work to empty the tank in 1 day ?

Discuss
Solution:
Let the required number of working hours per day be x
More pumps, Less working hours per day (Indirect proportion)
Less days, More working hours per day (Indirect proportion)
Pumps 4:3Days 1:2}::8:x
 4×1×x=3×2×8x=(3×2×8)(4)x=12
37. If 5 men or 7 women can earn Rs. 5250 per day, how much would 7 men and 13 women earn per day ?

Discuss
Solution:
Let the required earning be Rs. x
5 men = 7 women
7 men = (75×7)   women = 495 women
∴ (7 men and 13 women)
=(495+13)women=1145 women
Now, More women, More earning (Direct proportion)
 7:1145:: 5250:x7x=(1145×5250)7x=119700x=17100
38. 3 men or 6 women can do a piece of work in 20 days. In how days will 12 men and 8 women do the same work ?

Discuss
Solution:
Let the required number of days be x
3 men = 6 women
⇒12 men = (2 × 12) women = 24 women
∴ 12 men and 8 women = (24 + 8) women = 32 women
Now, More women, Less days (Indirect Proportion)
 32:6::20:xx=(6×2032)x=154x=334
39. 49 pumps can empty a reservoir in 612 days, working 8 hours a day. If 196 pumps are used for 5 hours each day, then the same work will be complete in ?

Discuss
Solution:
Let the required number of days be x
Then,
More pumps, Less days (Indirect proportion)
Less working hour/day, More days (Indirect proportion)
Pumps 196:49Working hour/day 5:8}::132:x
 196×5×x=49×8×132x=(49×8×132×1196×5)x=135x=235
40. 30 labourers working 7 hours a day can finish a piece of work in 18 days. If the labourers work 6 hours a day, then the number of labourers to finish the same piece of work in 30 days, will be ?

Discuss
Solution:
Let the required number of labourers be x
Less working hour/day, More labours (Indirect proportion)
More days, Less labourers (Indirect proportion)
Working hours/day 6:7Days 30:18}::30:x
6×30×x=7×18×306x=126x=21