<p>A 31 Composite score on the ACT is equivalent to an estimate about 2100-2150 on the SAT. That is slightly better than your actual SAT score by a mere 10 points so if you're submitting one, might as well submit the other one.</p>
<p>i'd send both if possible, but if you can only send one, i'd send just the ACT unless the schools require subject tests. in that case, you have to send the SAT scores anyway</p>