Question

Estimate. then, divide 45.15÷21 using the standard algorithm and check.

Answer 1

To estimate 45.15 divided by 21, round to 45 and 20 to get an estimate of 2.25. Using the standard algorithm, 45.15 divided by 21 is exactly 2.15. This result can be checked by multiplying 2.15 by 21, which equals 45.15, confirming the division.

Step-by-step explanation:

To estimate 45.15 ÷ 21, you might round 45.15 to 45 and 21 to 20. Then, 45 ÷ 20 is 2.25, so you'd expect the answer to be a little higher than 2.25 because 20 is smaller than 21. Now, let's perform the standard algorithm for division.

1. Divide 45 by 21, which goes 2 times. Write 2 above the 45.
2. Multiply 2 by 21, which is 42, and subtract it from 45 to get 3.
3. Bring down the 1 (from the decimal part), making it 31.
4. Divide 31 by 21, which goes 1 time. Write 1 next to the 2 above the division bar.
5. Multiply 1 by 21 and subtract from 31 to get 10.
6. Bring down the 5, making it 105.
7. Divide 105 by 21, which goes exactly 5 times.

Therefore, 45.15 ÷ 21 is approximately 2.15. We can check the result by multiplying 2.15 by 21:

2.15 × 21 = 45.15, confirming our division is correct.

Answer 2

2.15
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