Page 168 - Start Up Mathematics_8 (Non CCE)

3. Three workers can finish a construction work in 12, 18, 24 days respectively. How long will they take to
finish the construction work, if they all work together?
4. 15 boys earn ` 900 in 6 days. What will 12 boys earn in 7 days?
5. 10 men can prepare 20 toys in 3 days working 12 hours a day. In how many days will 24 men prepare
32 toys working 4 hours a day?
6. Ram can do a piece of work in 4 hours, Shyam and Laxman can do it in 3 hours, Ram and Laxman can
do it in 2 hours. How long would Shyam alone take to do it?

Thinking Skills

1. 8 men and 12 women can do a piece of work in 9 days. 10 men and 20 women can do the same work in
6 days. How long will 5 men and 15 women take to do it?
[Hint: (8 men + 12 women) complete the work in 9 days.
fi (72 men + 108 women) complete the work in 1 day.
(10 men + 20 women) complete the work in 6 days.
fi (60 men + 120 women) complete the work in 1 day.
Now, work of (72 men + 108 women) in 1 day = Work of (60 men + 120 women) in 1 day
fi 1 man’s work = 1 woman’s work]
2. The work done by a woman in 8 hours is equal to the work done by a man in 6 hours and the work done
by a boy in 12 hours. If working 6 hours per day, 9 men can complete a work in 6 days, then in how
many days can 12 men, 12 women and 12 boys together finish the same work working 8 hours per day?
3. To do a certain work, B would take three times as long as A and C together and C twice as long as A and
B together. The three men together complete the work in 10 days. How long would each take separately
to complete the work?
4. Two pipes A and B can fill a tank in 24 minutes and 32 minutes respectively. If both the pipes are opened
simultaneously, after how much time should B be closed so that the tank is full in 18 minutes?

Values and Life Skills

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1. Ram, Shyam and Mukesh can reap a field in days; Shyam, Mukesh and Chandu in 14 days; Mukesh,
4
Chandu and Ram in 18 days; Chandu, Ram and Shyam in 21 days. In how much time can all of them
together reap the field? What is the importance of team work?
2. A cistern which could be filled in 9 hours takes one hour more to be filled owing to a leakage in its bottom.
If the cistern is full, in what time will the leakage empty it? What should you do if there is a leakage in
the tank which store water at your home?

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