Rounded to three significant figures, 24/610 = 0.0393
24.4
0.0131
21.7857
61
610 mm
152.5
The square root of 610 lies between 24 and 25.
LCM of two numbers = their product divided by their HCF. The HCF of 64 and 610 is only 2 so the LCM is 64 x 610/2 ie 19520.
2.0833
80
24
7.5833