Sorry, You can't do the job with a 4-bit binary counter.(7493)
To devide by 50 You need at least a 6- bit binary counter!
Use 2 4-bit binary counters where output 4 from the first counter is connected to the clock of the second 7493.
feed outputs 2,5 and 6 to a 3 input nand. invert the output of the nand and feed this signal to the reset pins of
both counters and to your application (1 sec pulse).
Advice, Buy some modern stuf like the MC 4040 (12 bit counter)