The last method (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.)
Step-by-step explanation:
Option 1 is unreasonable because removing the decimal points just changes the whole problem and claims that Harshini rode her bike 1376 kilometers on Monday and etc., which she did not. Option 2 is unreasonable because not all the numbers are near 20 and should be rounded to their nearest whole numbers instead to find a more accurate estimate. Option 3 is unreasonable for the same reason as option 2, the numbers should be rounded to their nearest whole numbers instead to find a more accurate estimate. Option 4 is reasonable because the numbers are rounded to the nearest whole numbers which makes the estimate more accurate.
