td widths when table width is 100%

I need clarification on how the table cell widths should be calculated when you are using percentages.

Until now I have always calculated my cell widths so that their combined value equals the value of the table width.

ie.

<table width = “80%”><tr>
<td width = “50%”>
<td width =”30%”>
<tr></table>

However, recently I was challenged on this and it was suggested that the combined value of the table cell widths should always equal 100% and it is only the table width percentage that needs to be changed.

<table width=”80%”>
<td width = “63%”>
<td width =”37%”>
<tr></table>

Although I know this method can work, I’m not sure if its “good” code and I thought what I was doing was correct.
Please could someone clarify.

Any help appreciated.

Regards,

JsLady

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