Harshini rode her bicycle 13.76 kilometers on Monday, 9.8 kilometers on Wednesday, and 16.415 kilometers on Friday. She used the addition below to determine the total distance she rode over the three days.
13.76
9.8
+ 16.415
39.975
Which method determines whether her answer is reasonable?
Remove the decimal points and add 137 +98 + 16415 = 17,889; since 17,889 is not close to 39.975, her answer is
not reasonable.
Round all the numbers to 20; since 20 + 20 + 20 = 60 and 60 is not close to 39.975, her answer is not reasonable.
Round all the numbers to 10; since 10 + 10 + 10 = 30 and 30 is close to 39.975, her answer is reasonable.
Round 13.76 to 14, round 9.8 to 10, and round 16.415 to 16; since 14 + 10 + 16 = 40 and 40 is close to 39.975, her
answer is reasonable.