Round number of miles Bill rode each day to the nearst ten. Use the rounded numbers to show why it is not reasonable to say that he rode more than a total of 100 miles on Saturday and Sunday combined.

Question

Bill rode his bicycle 9 miles on Saturday. On Sunday, he rode his bicycle 4 times the number of miles he rode on Saturday.

Answer 1

The rules of rounding state that if the digit before the one you want to round to is 4 or less, you round down. If it is 5 or greater, you round up. As we are looking to round to the nearest 10, you need to look at the ones place. If you round the 9 miles Bill rode on Saturday to the nearest 10, you would get 10 miles. The miles he rode on Sunday would be rounded to 0. We can see that 10 miles is quite far from 100, so saying that Bill rode 100 miles over the weekend would not be a reasonable answer.