Key Points to Remember:
If A can do a piece of work in n days, then A's 1 day work is 1/n.
If A is thrice as good as B, then
(i) Ratio of work done by A to B is 3:1
(ii) Ratio of time taken by A and B is 1:3
Practice Questions:
Question 1:
Mahi takes 3 hours to complete a task and Sonu takes 7 hours to complete the same task. If Mahi and Sonu work together, how long will they take to complete the same?
Mahi's 1 hour work = 1/3
Sonu's 1 hour work = 1/7
Mahi + Sonu 's 1 hour work = 1/3 + 1/7 = 10/21
Hence Mahi and Sonu take 21/10 hours to complete if they work together.
21/10 = 2 1/10 hours or 2.1 hours
Question 2:
Yuvi and Cheeku together can complete a piece of work in 8 days. If Yuvi alone can do the same in 24 days, how long will Cheeku take time to complete?
Yuvi + Cheeku's 1 day work = 1/8
Yuvi's 1 day work = 1/24
Cheeku's 1 day work = (1/8) - (1/24) = 2/24
Hence Cheeku takes 24/2 = 12 days to complete the work.
Question 3:
Ziva is twice as good as Gracia and together they finish the piece of work in 20 days. In how many days will Ziva alone do the work?
Ziva's work : Gracia's work = 2:1
Ziva + Gracia's 1 day work = 1/20
Dividing 1/20 in the ratio of 2:1
Ziva's work = (1/20) * 2/3 = 1/30
Hence Ziva takes 30 days to complete the work.
(Task for the readers, find the days for Gracia to complete the work)
Question 4:
Ram can do a certain job in 16 days. Sam is 60% more efficient than Ram. How many days does Sam alone take to complete the task?
Ratio of times taken by Ram and Sam = 160:100 = 8:5
If Sam takes x days to complete the task,
Then,
8 : 5 :: 16 : x => 8x = 80
Hence, Sam takes, 10 days to complete the task.
Question 5:
Sakshi can do 1/4th of the work in 10 days. Priyanka can do 40% of the work in 40 days and Anushka can do 1/3rd of the work in 13 days. Who will complete the work first?
Sakshi's whole work = 10 * 4 = 40 days (as 1/4 = 25% of the work)
Priyanka's whole work = 40 * (100/40) = 100 days
Anushka's whole work = 13 * 3 = 39 days
Hence Anushka will complete the given work first.
Time to Think:
A man can do a job in 15 days. His father takes 20 days to complete and his son takes 25 days to do the same. How long it takes, if they all work together?
Hence Cheeku takes 24/2 = 12 days to complete the work.
Question 3:
Ziva is twice as good as Gracia and together they finish the piece of work in 20 days. In how many days will Ziva alone do the work?
Ziva's work : Gracia's work = 2:1
Ziva + Gracia's 1 day work = 1/20
Dividing 1/20 in the ratio of 2:1
Ziva's work = (1/20) * 2/3 = 1/30
Hence Ziva takes 30 days to complete the work.
(Task for the readers, find the days for Gracia to complete the work)
Question 4:
Ram can do a certain job in 16 days. Sam is 60% more efficient than Ram. How many days does Sam alone take to complete the task?
Ratio of times taken by Ram and Sam = 160:100 = 8:5
If Sam takes x days to complete the task,
Then,
8 : 5 :: 16 : x => 8x = 80
Hence, Sam takes, 10 days to complete the task.
Question 5:
Sakshi can do 1/4th of the work in 10 days. Priyanka can do 40% of the work in 40 days and Anushka can do 1/3rd of the work in 13 days. Who will complete the work first?
Sakshi's whole work = 10 * 4 = 40 days (as 1/4 = 25% of the work)
Priyanka's whole work = 40 * (100/40) = 100 days
Anushka's whole work = 13 * 3 = 39 days
Hence Anushka will complete the given work first.
Time to Think:
A man can do a job in 15 days. His father takes 20 days to complete and his son takes 25 days to do the same. How long it takes, if they all work together?
No comments:
Post a Comment