Long division answer diffrent to calculator

Hi guys,

I've got a bit of a problem with my long division - I was hoping you could help me with please. I keep getting a slight variation between my results on paper and the one I get from the calculator.

**Question: If a/c flies 764 miles in 78 mins how fast is it moving?**

S=D/t

So the equation I'd use is

S = (764 / 78) x 60 (to convert the minutes to hours).

The result I got from long division is 578MPH...

However using a calculator, the answer I got was more like 587MPH..

I've noticed this problem with pretty much any equation I do using long division.. The answer is always slightly different to that of the calculator mainly after the decimal point.

Before the x60 conversion, the decimal I had from long division (764 / 78 = 9.62) but the calculator's answer was more like 9.79.. which seems to make all the diffrence.

No matter what I do, I cant seem to replicate this answer using simple long division.

Am I doing this all wrong?