15 CHAP - 15. TIME AND WORK IIMPORTANT FACTS AND FORMULAE...

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15. TIME AND WORK IIMPORTANT FACTS AND FORMULAE 1. If A can do a piece of work in n days, then A's 1 day's work = (1/n). 2. If A’s 1 day's work = (1/n),then A can finish the work in n days. 3. A is thrice as good a workman as B, then: Ratio of work done by A and B = 3 : 1. Ratio of times taken by A and B to finish a work = 1 : 3. SOLVED EXAMPLES Ex. 1. Worker A takes 8 hours to do a job. Worker B takes 10 hours to do the same Job.How long should it take both A and B, working together but independently, to do the same job? (IGNOU, 2003) Sol. A’s 1 hour's work = 1/8 B's 1 hour's work = 1/10 (A + B)'s 1 hour's work = (1/8) +(1/10)=9/40 Both A and B will finish the work in 40/9 days. Ex. 2. A and B together can complete a piece of work in 4 days. If A alone can complete the same work in 12 days, in how many days can B alone complete that work? (Bank P.O. 2003) Sol . (A + B)'s 1 day's work = (1/4). A's 1 day's work = (1/12). B's 1 day's work =((1/4)-(1/12))=(1/6) Hence, B alone can complete the work in 6 days.
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Ex. 3. A can do a piece of work in 7 days of 9 hours each and B can do it in 6 days of 7 bours each. How long will they take to do it, working together 8 hours a day? Sol
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15 CHAP - 15. TIME AND WORK IIMPORTANT FACTS AND FORMULAE...

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