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NDA Math Circle
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© examsnet.com
Question : 9
Total: 26
The radius of a circle is increasing at the rate of
0.7
c
m
∕
s
e
c
.
What is the rate of increase of its circumference?
[NDA-I 2020]
4.4
c
m
∕
s
e
c
8.4
c
m
∕
s
e
c
8.8
c
m
∕
s
e
c
15.4
c
m
∕
s
e
c
Validate
Solution:
👈: Video Solution
Circumference of a circle
C
=
2
π
r
Differentiating both sides w.r.t. time
(
t
)
d
c
d
t
=
2
π
.
d
r
d
t
=
2
π
.
(
0.7
)
=
1.4
π
=
1.4
×
22
7
=
4.4
c
m
∕
s
e
c
© examsnet.com
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