If A and B together can complete a piece of work in 15 days and B alone in 20 days, in how many days can A alone complete the work?
A. 60
B. 45
C. 40
D. 30
Answer: Option A
Solution(By Examveda Team)
1st method:A and B complete a work in = 15 days
One day's work of (A + B) = $$\frac{1}{{15}}$$
B complete the work in = 20 days;
One day's work of B = $$\frac{1}{{20}}$$
Then, A's one day's work
$$\eqalign{ & = \frac{1}{{15}} - \frac{1}{{20}} \cr & = \frac{{4 - 3}}{6} \cr & = \frac{1}{{60}} \cr} $$
Thus, A can complete the work in = 60 days.
2nd method:
(A + B)'s one day's % work = $$\frac{{100}}{{15}}$$ = 6.66%
B's one day's % work = $$\frac{{100}}{{20}}$$ = 5%
A's one day's % work = 6.66 - 5 = 1.66%
Thus, A need = $$\frac{{100}}{{1.66}}$$ = 60 days to complete the work.
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Comments ( 4 )
Related Questions on Time and Work
A. 18 days
B. 24 days
C. 30 days
D. 40 days
1/15-1/20
Hw to solve
If given A+B=15 days
B=20 days
A=?
Sol:
Formula use xy/x-y
=15*20/15-20
=300/5
=60 so simple 😊
A+B =15
B= 20
Taking lcm we get 60 dividing 60 by 15&20 we get values 4 and 3.
4-3=1
A`s 1 day work =1
60 days work =60/1 = 60 days
why should we do in a fraction?? n what is that 1 day?