i already learned how the 60 seconds works with the ic mentioned in the title by applying an AND gate. But i dont know how when it comes to 24 seconds counting. Please help me, im just starting to study Logic Circuit.
Well for the 60 second counter you reset the tens digit to 0 when it counted to 6 (that's 0110 in binary, which is why the AND gate inputs connected to the 2nd and 3rd bit of the counter).
To reset at 24, you need to connect an AND gate such that its output is high when a value of 2 in on the tens digit and a value of 4 is on the ones digit. The AND gate output connects to the clear/reset lines of both counters.