I believe the answer would be 171.5 because the 343m/s is the speed but it only lasted for half a second so divide 343 by 2 and you get 171.5. hope this helps
81 if the number is higher than 5 or equal to 5 you round up
You divide the double digit divisor into the dividend. If the dividend is a double digit number too then you add a decimal and a zero to the dividend