Question

A 12 MHz clock frequency is applied to a cascaded counter containing a modulus-5 counter, a modulus-8 counter, and a modulus-10 counter. The lowest output frequency possible is ________

(a) 10 kHz

(b) 20 kHz

(c) 30 kHz

(d) 60 kHz

The question was posed to me by my school principal while I was bunking the class.

My doubt is from Counter ICs in section Counters of Digital Circuits

Answer 1

Right option is (c) 30 kHz

To elaborate: Cascaded counter containing a modulus-5 counter, a modulus-8 counter, and a modulus-10 counter. So, 5*8*10=400. Applied clock frequency = 12 MHz; hence, the lowest output frequency possible is 12MHz/400=30 kHz.