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Anonymous asked in Education & ReferenceHomework Help · 3 years ago

A contractor has to built a bridge in 50 days - SAt QUERY?

A contractor has to built a bridge in 50 days .Initially he employed 20 men but found that only half of the work has been completed in 30 days.How many more men does he have to employ to finish his job in time

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  • 3 years ago
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    There have been many different London Bridges on the same site over the past 2,000 years, which have indeed been knocked down, or fallen down, or destroyed in various ways, and the nursery rhyme alludes to this.

    The Romans built a few different bridges during their reign (including, ultimately, a stone bridge), but this fell into disrepair after the Romans left.

    During much of the Saxon era there was no need for a bridge crossing at this point as the river formed a political boundary between two hostile kingdoms. By all accounts the bridge was not reconstructed until sometime around 1000 AD, and this one was destroyed by Olaf II of Norway. A later Norman bridge was destroyed in a tornado in 1091, and its successor was at least partially destroyed by fire in 1136; some rebuilding work was carried out after that.

    The most famous and long-lived bridge on the site was the stone medieval bridge completed in 1209 during King John's reign. The King allowed shops and houses to be built on either side of the bridge, up to seven stories high, as a means of deriving revenue for the maintenance of the bridge. The bridge became very crowded due to this, and it meant that the bridge could take up to an hour to cross at busy times. Several disasters including fires and arch collapses befell the bridge, but it ultimately survived until 1831, when a new bridge designed by John Rennie opened alongside it and the old bridge was demolished.

    In 1924 it was realised that the lifespan of the bridge was limited (it was sinking!) and it would eventually have to be replaced. In 1967 the City of London Council came up with the idea of putting the old bridge up for sale; the American entrepreneur Robert P. McCulloch bought it for $2,460,000 with the intention of reconstructing it in Arizona. The bridge that now spans the Bridgewater Channel canal at Lake Havasu is not entirely the original structure - it consists of a concrete frame with cladding stones taken from the original bridge. The remaining stones were stored in a quarry in Devon and some of these were auctioned online in 2003.

    There is an urban legend that McCulloch actually thought he was buying the much grander Tower Bridge, which some people mistakenly think of as London Bridge, but he has denied this in interviews.

    A new London Bridge opened in 1973, and this bridge still stands today, carrying commuters across the river in the same spot that the Romans built their first wooden bridge nearly 2,000 years ago.

  • 3 years ago

    Each man builds (1/2)(1/30)(1/20) = 1/1200 of the bridge per day.

    He has 20 days left and he needs to build 1/2 the bridge.

    Let x = the number of men he needs to build the other 1/2. (this will not be your answer).

    (1/1200) * 20 * x = 1/2

    x = 30 men

    Now the answer to the question is either 30 men total or he has to hire 10 more. It depends on how the choices go. thirty looks better to me.

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