If untimed accuracy is already decent, your first priority is probably pacing rather than relearning the underlying math. Break the problem into reading time, setup time, calculation time, and decision time to see where the seconds are actually going.

Use short timed sets instead of only full tests. Practice moving on when a question is consuming too much time, then review whether the issue was calculation speed, setup, or reading the data.

Do not chase speed by rushing every question. The goal is to protect easy points while preventing one difficult item from damaging the rest of the section. If useful, this guide on Bain TestGorilla guide gives more detail.

same problem. untimed score looked fine, timer destroyed me.

I fixed question selection before trying to get faster at every calc. biggest gain for me.