Chain Rule

If 15 men, working 9 hours a day, can reap a field in 16 days, in how many days will 18 men reap the field, working 8 hours a day? A)18 B)20 C)15 D)13 Answer : Option C Explanation: Let the required number of days be x. More men, Less days (indirect proportion) Less hours per day, More days (Indirect proportion) Men 18 : 15 Hours per day 8: 9 = 16 : X (18 x 8 x X)=(15 x 9 x 16) => X=(2160)/144 = 15 Hence, required number of days = 15. Q 10: 4 mat-weavers can weave 4 mats in 4 days. At the same rate, how many mats would be woven by 8 mat-weavers in 8 days? A)15 B)14 C)12 D)16 Answer : Option D Explanation: 4 weavers 4 mats in 4 days 8 weavers ? mats in 8 days 1 weaver 1 mat in 4 days 1 weaver 2 mats in 8 days 8 weaver (8*2) 16 mats in 8 days Q 11: If 30 children can do a piece of work in 20 hours, then in how many hours will 12 children do it? A)40 hours B)55 hours C)50 hours D)52 hours Answer : Option C Explanation: Let the number of hours be x. 12 : 30 = 20 : x 12/30=20/x x=(20x30)/12=50 hours Q 12: An industrial loom weaves 0.128 meter of cloth every second. Approximately, how many seconds will it take for the loom to weave 25 meter of cloth ? A)195.31 seconds B)185.36 seconds C)155.31 seconds D)None of these Answer : Option A Explanation: Let the time required by x seconds. Then, More cloth means More time (Direct Proportion) So, 0.128:1=25:x =>x=(25x1)/0.128 =>x=195.31

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