Ned calculated 17÷4=4.25 .use estimation to see if his answer is reasonable . how can you check his exact answer

You can use estimation by saying that 4 * 4 = 16 and 4 * 5 = 20
therefore your number has to be less that 5 but slightly greater than 4.
you can check his exact answer by doing division or checking it on a calculator.

hope this helps :)