Solution: H.C.F. of three numbers is = H.C.F. of[H.C.F. of any two)and (the third number)].
H.C.F. of two numbers can be calculated as described as follows "Divide the larger number by the smaller number.
Now divide the divisor by the remainder.
Repeat the process of dividing the preceding number by the remainder last obtained till zero is obtained as remainder.
The last divisor is the required H.C.F." by calculating we get 100 as H.C.F. of 1000 and 24300. then find H.C.F. of 100 and 360. we will get 20.
Hence required H.C.F is 20.