SSC CHSL Model Paper 1

Question : 38 of 100

Marks: +1, -0

The diameter of two circles are 18 cm and 8 cm.
The distance between their centres is 13 cm.
What is the number of common tangents?

Solution:

Here,

r _1 = 9

cm and

r_2 = 4

r _1 + r_2 = 9 + 4 = 13\cm

and

r _1-r_2 = 9 -4 = 5\cm

Also, d = 13 cm
Here,

d = r_1 + r_2

= 13 cm
Hence, two circles touch each other externally, so there are three common tangents.

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