Question

Andrea wanted to know how much farther she ran on Tuesday than on Monday. Her work is below.

A student showing work for 4.705 minus 3.6 = 4.669. The decimal for 3.6 is between the 0 and 5 in 4.705.

What mistake did Andrea make when solving the problem?
She did not align the decimal points.
She did not rename correctly.
She added instead of subtracted.
She did not subtract 15 and 6 correctly.

Answer 1

Andrea's mistake was in incorrectly aligning the decimal points in her subtraction sum. Once the decimal points are correctly aligned, you subtract 3.6 from 4.705 to get the correct result of 1.105.

Step-by-step explanation:

Andrea made an error in her calculation when trying to find out how much farther she ran on Tuesday than on Monday. The mistake she made was not correctly aligning the decimal points when she subtracted 3.6 from 4.705. The result she got, 4.669, does not make sense because the number subtracted (3.6) is larger than the difference she got (4.669).

Her decimal for 3.6 should not be placed between the 0 and 5 in 4.705. Instead, the decimal points should line up. After correctly aligning the decimals, the calculation should look like:

4.705 - 3.6 = 1.105

So Andrea ran 1.105 km more on Tuesday than on Monday.

Learn more about Decimal Subtraction