Answer:
a)7640
b)4325670
Step-by-step explanation:
when rounding off a number one of the factors to consider is the number before the number you are supposed to round off,if the number is greater than 5 or equal to then you can go ahead and add a 1 to the number you have to round off.but if the number before is less than 5 you just have to leave the number the way it is.in this case for the first question you can see that the tens number is 3 and the number before is greater than 5 so you can add a 1 to the 3 to make it 4, bringing the answer to 7640 the 9 becames a zero..for the second one you can see that the number before the tens number is less than 5 so you can't add a 1 to it leaving the answer as 4325670..
I hope this helps
