waecmaths question:
In the diagram, the two circles have a common a centre O, if the area of the larger circle is 100π and that of the smaller circle is 49 π. Find x
Option A:
2
Option B:
3
Option C:
4
Option D:
5
waecmaths solution:
$A=\pi r_{2}^{2}-\pi r_{1}^{2}=\pi (r_{2}^{2}-r_{1}^{2})$
${{A}_{2}}=\pi r_{2}^{2}=100\pi c{{m}^{2}}$
$r_{2}^{2}=100c{{m}^{2}},\text{ }{{r}_{2}}=10cm$
$r_{1}^{2}=49c{{m}^{2}},\text{ }r=7cm$
$x={{r}_{2}}-{{r}_{1}}=10cm-7cm=3cm$
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