Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 1)
1.
A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is :
Answer: Option
Explanation:
| A's 1 day's work = | 1 | ; |
| 15 |
| B's 1 day's work = | 1 | ; |
| 20 |
| (A + B)'s 1 day's work = |  |
1 | + | 1 |  |
= | 7 | . |
| 15 | 20 | 60 |
| (A + B)'s 4 day's work = | |
7 | x 4 | |
= | 7 | . |
| 60 | 15 |
| Therefore, Remaining work = | |
1 - | 7 | |
= | 8 | . |
| 15 | 15 |
Discussion:
344 comments Page 14 of 35.
Sid said:
1 decade ago
LCM 15, 20 will give you 60 (the total work).
LCM of 15 and 20,
5*3 = 15.
5*4 = 20.
THEREFORE, 3*4*5 = 60.
1 day work of A = 60/15 = 4.
1 day work of B = 60/20 = 3.
1 day work of A and B together = 4 + 3 = 7 / 60.
A and B worked together for 4 days = 4 * 7/60 = 28/60 = 7 / 15.
Therefore,
Work left = Total work - Work done in 4 days by A and B together.
Work left (IN FRACTIONS) = 1 - 7/15 = (15-7)/15 = 8/15.
Thank you for giving me an opportunity.
LCM of 15 and 20,
5*3 = 15.
5*4 = 20.
THEREFORE, 3*4*5 = 60.
1 day work of A = 60/15 = 4.
1 day work of B = 60/20 = 3.
1 day work of A and B together = 4 + 3 = 7 / 60.
A and B worked together for 4 days = 4 * 7/60 = 28/60 = 7 / 15.
Therefore,
Work left = Total work - Work done in 4 days by A and B together.
Work left (IN FRACTIONS) = 1 - 7/15 = (15-7)/15 = 8/15.
Thank you for giving me an opportunity.
L raj Scope said:
1 decade ago
How to come [1/15+1/20] = 7/60?
Prasanth.sunny143 said:
1 decade ago
@L Raj Scope
Please understand this concept first.
LET CONSIDER A SIMPLE STATEMENT:
A can do a work in 2 days.
That means A's 1 day work = 1/2.
This is the methodology we wanna apply on the data which is given in question.
From the question.
A (CAN D0 A JOB) ----15 days.
B (CAN DO A JOB) ----20 days.
Therefore by the above concept A's 1 day work = 1/15.
B's 1 day work = 1/20.
Therefore both A&B 1 work = (1/15)+1/20) = 7/60.
NOW READ THE QUESTION.
If A&B work together for 4 days then what the fraction of work left.
Consider:
Total work = 1.
A&B (4 DAYS WORK) = (7/60)*4 = 7/15.
REMAIN B WORK = (TOTAL WORK)-(COMPLETED WORK BY A&B FOR 4 DAYS).
= 1-7/15.
= 8/15.
Hope this is helpful.
Please understand this concept first.
LET CONSIDER A SIMPLE STATEMENT:
A can do a work in 2 days.
That means A's 1 day work = 1/2.
This is the methodology we wanna apply on the data which is given in question.
From the question.
A (CAN D0 A JOB) ----15 days.
B (CAN DO A JOB) ----20 days.
Therefore by the above concept A's 1 day work = 1/15.
B's 1 day work = 1/20.
Therefore both A&B 1 work = (1/15)+1/20) = 7/60.
NOW READ THE QUESTION.
If A&B work together for 4 days then what the fraction of work left.
Consider:
Total work = 1.
A&B (4 DAYS WORK) = (7/60)*4 = 7/15.
REMAIN B WORK = (TOTAL WORK)-(COMPLETED WORK BY A&B FOR 4 DAYS).
= 1-7/15.
= 8/15.
Hope this is helpful.
(3)
Aravind said:
1 decade ago
Why calculate the remaining work (1-7/15) ? The question ask to find the fraction left.
Tricky said:
1 decade ago
Efficiency Method:
Total 60 unit.
A = 60/15 = 4.
B = 60/20 = 3.
Total = 7/60.
In 4 days = 4*7/60 = 28/60 = 7/15.
Remain = 1-7/15 = 8/15.
Total 60 unit.
A = 60/15 = 4.
B = 60/20 = 3.
Total = 7/60.
In 4 days = 4*7/60 = 28/60 = 7/15.
Remain = 1-7/15 = 8/15.
Vaibhav said:
1 decade ago
Why 1-7/15?
The total no. of work is 1 do 1-7/15.
If there are 2 works then 2-7/15.
If 3 works then 3-7/15.
And so on.
The total no. of work is 1 do 1-7/15.
If there are 2 works then 2-7/15.
If 3 works then 3-7/15.
And so on.
Sabaneak said:
1 decade ago
If remaining work is 8/15, how many days will it take A alone to complete the work.
Sweety said:
1 decade ago
A's 1 day's work = 1/15.
B's 1 day's work = 1/20.
(A + B) 's 1 day's work = (1+1) = 7.
15 20 60.
(A + B) 's 4 day's work = (7x1) = 7.
60 4 15.
Therefore, Remaining work = (1+7) = 8.
15 15.
B's 1 day's work = 1/20.
(A + B) 's 1 day's work = (1+1) = 7.
15 20 60.
(A + B) 's 4 day's work = (7x1) = 7.
60 4 15.
Therefore, Remaining work = (1+7) = 8.
15 15.
Aravind_appu said:
1 decade ago
A = 1/15.
B = 1/20.
Together TH = A+B.
TH = (1/15+1/20).
TH/4 = (1/15+1/20).
TH = 4((35/15*20)).
TH = 7/15.
= 1-7/15 = 8/15.
B = 1/20.
Together TH = A+B.
TH = (1/15+1/20).
TH/4 = (1/15+1/20).
TH = 4((35/15*20)).
TH = 7/15.
= 1-7/15 = 8/15.
Anand said:
1 decade ago
Balance work = 8/15.
A = 1/15, B = 1/20.
Total no of days required to complete remaining work.
A = (8/15) / (1/15) = 8 days,
B = (8/15) / (1/20) = 10 2/3 days.
A = 1/15, B = 1/20.
Total no of days required to complete remaining work.
A = (8/15) / (1/15) = 8 days,
B = (8/15) / (1/20) = 10 2/3 days.
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