Going through long division: We see that 21 goes into 52 twice, with a remainder of 10. Bringing down the first 0 after '21,' we have '100' to divide by 21; the quotient is 4 and the remainder 16. Bringing down the 2nd '0' after 21, we now have '160' to divide by 21; the quotient is 7 with a remainder of 13. So far we have 2.47 as our quotient. We can continue this process as far as desired.
Divide 21 into 52 with a calculator to check your work here.
52 divided by 21 is 2.48 after rounding up.