tinn asked in Science & MathematicsMathematics · 8 years ago

# 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?

Relevance
• 8 years ago

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

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