Question

Explain how to find 398 + 257 with mental math and with the standard algorithm.

Answer 1

To find the sum of 398 + 257, you can use mental math or the standard algorithm. When using mental math, break down the numbers and simplify the addition. With the standard algorithm, line up the numbers and add the digits in each place value.

Step-by-step explanation:

To find the sum of 398 + 257 using mental math, you can break down the numbers into easier parts. Start by adding 400 and 200, which equals 600. Then, subtract 2 from 400 and 57 from 200, which gives you 398 + 200 - 57 - 2. Simplify this to 600 - 59, which equals 541. Therefore, 398 + 257 is equal to 541.

To find the sum of 398 + 257 using the standard algorithm, you can line up the numbers vertically and add the digits in each place value. Start with the ones place and add 8 + 7, which equals 15. Write down the 5 and carry over the 1. Then, add 9 + 5 (plus the carried-over 1), which equals 15. Write down the 5 and carry over the 1. Finally, add 3 + 2 (plus the carried-over 1), which equals 6. The final sum is 641. Therefore, 398 + 257 is equal to 641.

Answer 2

Step-by-step explanation:

If you were to round 398 to the nearest hundred, you would get 400. that's only 2 off of 398. when you add 400 + 257 that would equal 857 because 4 + 2= 6 and then the other two digits on 400 are zeros so 5 and 7 stay the same. with 857, you must now subtract 2 because you added 2 earlier. 857 - 2 = 855.