(exp)to be quick to take a hint; to be very responsive; to be quick on the uptake
彼とはツーと言えばカーの仲だよ。以心伝心の仲とでも言っておこう。 He and I have a near-telepathic understanding of each other. No sooner does one of us say something than the other is already responding.
Nowadays, however, calculators can be used freely in school examinations, and already in many schools the only sound to be heard during a math exam is the sound of children tapping on their calculators.
Japanese Dictionary
