It takes a man one hour to mow his lawn. It takes his son 90 minutes to mow the same lawn.?

How long will it take if father and son work together to mow the lawn?

9 Answers

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  • 8 years ago
    Favorite Answer

    rate multiplied by time equals work done

    rate of father is 1/60

    rate of sone is 1/90

    together (1/60 + 1/90)

    to solve for time

    (1/60 + 1/90)(x) = 1 (since only one mow is lawned)

    hence x= 5400 / 150

    or basically 36 minutes

    Source(s): my math skills
  • 8 years ago

    It will take 75 minutes because, guess what!, they only have one lawn-mower!

    So the man mows half the lawn in 30 minutes, then the son mows the other half of the lawn in 45 minutes: 30 + 45 = 75 minutes.

  • 3 years ago

    how plenty do they mow in a million hour Jack = a million/6 Marilyn = a million/3 time = x x/6 + x/3 = a million discover consumer-friendly denominator x/6 + 2x/6 = 6/6 x + 2x = 6 3x=6 divide by using 3 on the two ingredient x=2 they are going to take 2 hours to mow the backyard at the same time

  • Como
    Lv 7
    8 years ago

    Let`s be civilised and go metric !

    Let area of lawn be X m ²

    father`s rate of work = X / 60 m ² / min

    son`s rate of work = X / 90 m ² / min

    Combined rate = X/60 + X/90 m ² / min = 5X/180 m ² / min

    Time for both working together is given by :-

    Area / rate = X / [ 5X/180 ] min = 180/5 min = 36 min

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  • DWRead
    Lv 7
    8 years ago

    father's speed = 1 lawn/hour

    son's speed = 1 lawn/1.5 hours = 2/3 lawn/hour

    combined speed = (1+2/3) lawn/hour = 5/3 lawn/hour = 3/5 hour/lawn

    3/5 hour × 60 minutes/hour = 36 minutes

  • Anonymous
    8 years ago

    time=1/ ((1/60)+(1/90))

    = 36 minutes

  • 8 years ago

    (60*90)/(60+90)= 36 mins

  • Anonymous
    8 years ago

    45 minutes.

  • 8 years ago

    It depends on whether they have more than one lawnmower.

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