TJ Prep Problems

TJ test prep practice problems  for our students and readers. The problems provide a very small sampling of what Optimal TJ Prep students work with.

An arithmetic Problem for TJ/Blair/AOS Prep (Medium). Target Time 30-50 seconds.

A Hybrid car requires 12000 Kilo Joules of charge. There are 2 chargers available: A fast charger which can charge 400 Joules/second (and should be used after midnight) and a slow charger which can only charge 100 Joules/second. Robert starts charging his car at 8 PM. At midnight fast charger kicks in and both chargers continue charging until the car is totally charged. At what time, Robert's car will be fully charged?