An id
selector is more specific than a class
selector so will be applied last in the cascade.
id
s have to be unique, so your HTML is invalid anyway. Use classes throughout instead.
<div class="num first">0</div>
<div class="num">1</div>
<div class="num">4</div>
<div class="num">6</div>
<div class="num last">9</div>