Ans: 28% <br />
<!--#perl sub="HTML::TeX" arg="
The area of the larger circle is 25\$ \pi \$ cm \$^2\$.
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The area of the smallest circle is 9\$ \pi \$ cm \$^2\$.
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The area of the middle circle is 16\$ \pi \$ cm \$ ^2 \$.
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Therefore the area of the ring is (16\$ \pi \$ - 9 \$ \pi \$) cm \$ ^2 \$ i.e. 7\ $ \pi \$
 cm \$^2 \$.
"-->
<br />
Therefore the percentage shaded is 28%. <br />