(1) Ritu can row downstream 20 km in 2 hours, and upstream 4 km in 2 hours. Find her
speed of rowing in still water and the speed of the current.
women and 5 men can together finish an embroidery work in 4 days, while 3
Answers
Answer:
rithu is my friend's name
Step-by-step explanation:
who wrote this question
Answer
(i) Let her speed in still water be x and speed of stream be y
Now, According to question and using time =
speed
distance
⇒
x+y
20
=2 and
x−y
4
=2
⇒x+y=10;x−y=2
⇒On solving we get x=6andy=4
⇒speed of Ritu in still water is 6km/hr and that of a stream is 4km/hr.
(ii)
Let the one woman do x unit work in one day and man do y unit
Now according to question,
⇒2×x×4+5×y×4=1 (i)
⇒3×x×3+6×y×3=1 (ii)
⇒8x+20y=1;9x+18y=1
Multiply equation (i) by 9 and (ii) by 8 then we have
⇒72x+180y=9;72x+144y=8
On solving we have
⇒y=
36
1
that is one man can finish that work in 36days
⇒x=
18
1
that is one woman can finish that work in 18days
(iii)
Let the speed of bus bex and that of train be y
Now, according to question and using time =
speed
distance
⇒
y
60
+
x
240
=4⇒
y
15
+
x
60
=1 (i)
⇒
y
100
+
x
200
=
6
25
⇒
y
24
+
x
48
=1 (ii)
From (i)
⇒
x
1
=
60
1
(1−
y
15
) putting this in eq (ii)
⇒
y
24
+
60
48
(1−
y
15
)=1
⇒
y
24
+
5
4
−
y
12
=1
⇒∴y=60km/hr
then x=80km/hr