Page 142 - Maths Skills - 8

140 Maths

Hence, Aditya’s one day work = (Aditya and Manav’s 1 day work) – (Manav’s 1 day work)

51- 4 2
= 1 - 1 = = =
6 30 30 30 15
Aditya can do 2 work in 1 day.
15
2 15 1
Aditya can do the whole work in 1 ÷ days = 1× days = 7 days
15 2 2
1
Hence, Aditya can alone complete the work in 7 days.
2
Example 4: Five persons working 8 hours a day can do a piece of work in 18 days. How many persons will
complete it working 9 hours a day in 10 days.

Solution: Persons required to finish the work in 18 days working 8 hours a day = 5
Persons required to finish the work in 1 day working 8 hours a day Alternative Method
= 5 × 18 (less day, more persons) Days Time Men

Persons required to finish the work in 10 day working 8 hours a day 18 8 5
518× 10 9 x
= (More days, less persons) 18 8 x
10 Here,
Persons required to the work in 10 day working 1 hours a day 10 9 5
2
5188× × 18 ×× 5
8
= (Less hours, more persons) x =
10 10 × 9
Persons required to finish the work in 10 day working 9 hours a day = 8 men
5188× ×
= (More hours, less persons)
10 × 9
= 8

Exercise 9.3

1. Arun can finish a work in 4 days and Varun can finish the same work in 8 days. Find the number of days
required by Arun and Varun to finish the work, if they work together.
2. 54 girls make 270 garlands in 1 hour. How many garlands will 9 girls make in 3 hours?
3. A can do a piece of work in 40 days and B in 45 days. They work together for 10 days and then B goes
away. In how many days will A finish the remaining work?
4. A and B together can paint a room in 18 days. They work together for 8 days and then B goes away.
A finishes the rest of work in 15 days. How long would each take to finish the work separately?
5. Raza can do a piece of work in 5 days, Abdul can do the same work in 10 days and Karim can do it in
15 days. If all three work together, in how many days can they finish the job?
6. A, B and C can do a piece of work in 10, 9 and 15 days respectively. They started the work together, but
C left after 2 days. In how many days will the remaining work be completed by A and B?

7. P and Q can harvest a field in 5 and 7 days respectively. After P has worked for 3 days, he is joined by
Q. In how many more days will the work be completed?

8. P, Q and R together can build a house in 8 days. P and Q can build the house separately in 20 days and
24 days respectively. In how many days can R build the house alone?