Overview Exercise "If you judge people, you have no time to love them."
- Mother Teresa
16.
X and Y can do a piece of work in 20 days and 12 days respectively. X started the work alone and then after 4 days Y joined him till the completion of the work. How long did the work last?
Answer: B
Explanation:
Work done by X in 4 days =
1
x 4
=
1
.
20
5
Remaining work =
1 -
1
=
4
.
5
5
(X + Y)'s 1 day's work =
1
+
1
=
8
=
2
.
20
12
60
15
Now,
2
work is done by X and Y in 1 day.
15
So,
4
work will be done by X and Y in
15
x
4
= 6 days.
5
2
5
Hence, total time taken = (6 + 4) days = 10 days.
17.
A is 30% more efficient than B. How much time will they, working together, take to complete a job which A alone could have done in 23 days?
Answer: B
Explanation:
Ratio of times taken by A and B = 100 : 130 = 10 : 13.
Suppose B takes x days to do the work.
Then, 10 : 13 :: 23 : x x =
23 x 13
x =
299
.
10
10
A's 1 day's work =
1
;
23
B's 1 day's work =
10
.
299
(A + B)'s 1 day's work =
1
+
10
=
23
=
1
.
23
299
299
13
Therefore, A and B together can complete the work in 13 days.
18.
Ravi and Kumar are working on an assignment. Ravi takes 6 hours to type 32 pages on a computer, while Kumar takes 5 hours to type 40 pages. How much time will they take, working together on two different computers to type an assignment of 110 pages?
A. 7 hours 30 minutes B. 8 hours C. 8 hours 15 minutes D. 8 hours 25 minutes
Answer: D
Explanation:
Number of pages typed by Ravi in 1 hour =
32
=
16
.
6
3
Number of pages typed by Kumar in 1 hour =
40
= 8.
5
Number of pages typed by both in 1 hour =
16
+ 8
=
40
.
3
3
110 x
3
hours
40
= 8
1
hours (or) 8 hours 15 minutes.
4
19.
A, B and C can complete a piece of work in 24, 6 and 12 days respectively. Working together, they will complete the same work in:
Answer: B
Explanation:
Formula: If A can do a piece of work in n days, then A's 1 day's work =1
.
n
(A + B + C)'s 1 day's work =
1
+
1
+
1
=
7
.
24
6
12
24
Formula: If A's 1 day's work =1
,
then A can finish the work in n days.
n
So, all the three together will complete the job in
24
=
3
3
days.
7
7
20.
Sakshi can do a piece of work in 20 days. Tanya is 25% more efficient than Sakshi. The number of days taken by Tanya to do the same piece of work is:
Answer: D
Explanation:
Ratio of times taken by Sakshi and Tanya = 125 : 100 = 5 : 4.
Suppose Tanya takes x days to do the work.
5 : 4 :: 20 : x x =
4 x 20
5
x = 16 days.
Hence, Tanya takes 16 days to complete the work.
x =
Time taken by both to type 110 pages =