Answer :
Final answer:
Amal erred by improperly decomposing and combining the hundreds place when adding 378 and 141. The right way is to decompose the numbers into hundreds, tens, and ones, then add each place value separately, giving the correct sum of 519, not 400.
Explanation:
Amal made a mistake in her addition by incorrectly decomposing and adding the hundreds place of the two numbers. Decomposing numbers is a useful strategy in addition, but it must be applied accurately. Proper decomposition of 378 and 141 involves separating each number into hundreds, tens, and ones before adding, which should look like this:
300 + 100 = 400 (correct)
70 + 40 = 110 (incorrect in Amal's operation)
8 + 1 = 9 (correct)
To get the correct sum, you add these results:
400 (from the hundreds place)
110 (from the tens place)
9 (from the ones place)
The corrected addition looks like this:
400 + 110 + 9 = 519
Therefore, the correct sum of 378 and 141 is 519, not 400 as Amal wrote.
