You should not write 2636231974 as the answer. If you do, you are stating that you know the answer to 10 digits, but you don’t. The top two numbers going into the calculation were each known to 3 digits, and the bottom number was known to 6 digits. The answer is only known to the same number of digits as the least well known of the numbers going into the calculation, so in this case that is 3. The answer should be written in scientific notation and its coefficient should have 3 digits, 2.64, rounding up the last digit because the digit following it is greater than 5. The exponent is then the number of places the decimal point has to be moved going from the number to the coefficient, in this case that is 9 places to the left. So the number should be written as: