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Standard IX

Mathematics

Area of a Rectangle

In the given ...

Question

In the given figure, $C (O, r)$ and $C^{'} (O^{'}, r^{'})$ are two circles touching externally with $r = 9$ cm and $r^{'} = 4$ cm, then length of $A B$ is

12

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Solution

The correct option is A $12$ cm
From figure it is clearly evident that,
$(A B)^{2} = (r + r^{'})^{2} - (r - r^{'})^{2} = 4 r r^{'} = 4 \times 4 \times 9 = 144$
$\to A B = 12 c m$

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In the given figure, C(O,r) and C′(O′,r′) are two circles touching externally with r=9 cm and r′=4 cm, then length of AB is

The correct option is A 12 cmFrom figure it is clearly evident that,(AB)2=(r+r′)2−(r−r′)2=4rr′=4×4×9=144→AB=12cm

In the given figure, $C (O, r)$ and $C^{'} (O^{'}, r^{'})$ are two circles touching externally with $r = 9$ cm and $r^{'} = 4$ cm, then length of $A B$ is

The correct option is A $12$ cm
From figure it is clearly evident that,
$(A B)^{2} = (r + r^{'})^{2} - (r - r^{'})^{2} = 4 r r^{'} = 4 \times 4 \times 9 = 144$
$\to A B = 12 c m$