Let's go back to basics.
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What's 17% of 100 cm?
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17 centimers, DUH.
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So now what?
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DON'T PANIC!!
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The Ultimate Question to the Universe (ok math) will be answered shortly.
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700 cm is just 100 cm multiplied by 7, am I right?
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Good.
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So, multiply 17 by 7.
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Simple.
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And?
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You're done! See?
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Hope I helped!
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Any more question, ASK AWAY!!