Discuss Forum
1. X,Y and Z can do a piece of work in 6 hours.X and Y can do the same work in 8 hours and Y and Z can do the same work in 12 hours.In how many times will X and Z do the same work?
- A. 6 hours
- B. 6 hours
- C. 6 hours
- D. 6 hours
Answer: Option B
Explanation:
X + Y + Z can do 1/6 of job in one hour……1
X + Y can do 1/8 of job in one hour……2
Y + Z can do 1/12 of job in one hour……3
adding 2&3 we get
X + Y + Y + Z = 1/8 + 1/12
X + Z + 2Y = 5/24…4
subtracting 1 from 4 we get
Y = 5/24 – 1/6 = 1/24.substituting the value of Y in 4 we have
X + Z + 2/24 = 5/24
X + Z = 5/24 – 2/24 = 3/24 = 1/8
hence X&Z will do 1/8 of job in one hour.
So X & Z will do the work in 8 hours.
X + Y can do 1/8 of job in one hour……2
Y + Z can do 1/12 of job in one hour……3
adding 2&3 we get
X + Y + Y + Z = 1/8 + 1/12
X + Z + 2Y = 5/24…4
subtracting 1 from 4 we get
Y = 5/24 – 1/6 = 1/24.substituting the value of Y in 4 we have
X + Z + 2/24 = 5/24
X + Z = 5/24 – 2/24 = 3/24 = 1/8
hence X&Z will do 1/8 of job in one hour.
So X & Z will do the work in 8 hours.
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