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Chain-Rule
1.3 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?

Answer:Option 1

Explanation:

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)
Pumpu 4:3Days1:2}::8:x

4×1×x=3×2×8x=(3×2×8)(4)x=12

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2.If the cost of x metres of wire is d rupees, then what is the cost of y metres of wire at the same rate?

Answer:Option 1

Explanation:

Solution:
Cost of x metres=RsdCoast of 1 metre=Rs.(dx)Cost of y metres=Rs.(dx×y)=Rs.(ydx)

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3.Running at the same constant rate, 6 identical machines can produce a total of 270 bottles per minute. At this rate, how many bottles could 10 such machines produce in 4 minutes?

Answer:Option 1

Explanation:

Solution:
Let the required number of bottles be x.
More machines, More bottles (Direct Proportion)
More minutes, More bottles (Direct Proportion)
Machines4:3Time(in min.)1:2}::270:x

6×1×x=10×4×270x=(10×4×270)(6)x=1800

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4.39 persons can repair a road in 12 days, working 5 hours a day. In how many days will 30 persons, working 6 hours a day, complete the work?

Answer:Option 1

Explanation:

Solution:
Let the required number of days bex.
Less persons, More days (Indirect Proportion)
More working hours per day, Less days (Indirect Proportion)
Persons 30:39Working hour/day 6:5}::12:x

30×6×x=39×5×12x=(39×5×12)(30×6)x=13

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5.A man completes 5/8 of a job in 10 days. At this rate, how many more days will it takes him to finish the job?

Answer:Option 1

Explanation:

Solution:
Workdone=58Balancework=(158)=38LettherequirednumberofdaysbexThen,58:38=::10:x58×x=38×10x=(38×10×85)x=6

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6.If a quarter kg of potato costs 60 paise, how many paise will 200 gm cost?

Answer:Option 1

Explanation:

Solution:
Lettherequiredweightbexkg.Lessweight,lesscost(DirectProportion)250:200::60:x250×x=(200×60)x=(200×60)250x=48

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7.In a dairy farm, 40 cows eat 40 bags of husk in 40 days. In how many days one cow will eat one bag of husk?

Answer:Option 1

Explanation:

Solution:
Let the required number of days be x.
Less cows, More days (Indirect Proportion)
Less bags, Less days (Direct Proportion)
Cows1:40Bags40:1}::40:x

1×40×x=40×1×40x=40

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8.If 7 spiders make 7 webs in 7 days, then 1 spider will make 1 web in how many days?

Answer:Option 1

Explanation:

Solution:
Let the required number days be x.
Less spiders, More days (Indirect Proportion)
Less webs, Less days (Direct Proportion)
Spiders1:7Webs7:1}::7:x

1×7×x=7×1×7x=7

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9.A flagstaff 17.5 m high casts a shadow of length 40.25 m. The height of the building, which casts a shadow of length 28.75 m under similar conditions will be:

Answer:Option 1

Explanation:

Solution:
Let the height of the building x metres.
Less lengthy shadow, Less in the height (Direct Proportion)
40.25:28.75::17.5:x40.25×x=28.75×17.5x=28.75×17.540.25x=12.5

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10.In a camp, there is a meal for 120 men or 200 children. If 150 children have taken the meal, how many men will be catered to with remaining meal?

Answer:Option 1

Explanation:

Solution:
There is a meal for 200 children
150 children have taken the meal
Remaining meal is to be catered to 50 children
Now,
200 children = 120 men
∴ 50 children
=(120200×50)men=30 men

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