Here is the question: Give an estimate for the following expression. Then state whether you believe that the exact answer is greater than or less than the estimate. Explain how you decided, The original question is this 54*23. Here is what I've answered: 50*20. I rounded down. 54 went to 50 and 23 to 20. 54*23=1242 50*20=1000. The exact answer is greater than the estimate. I rounded 12 to 10 and 26 to 30.
Yes, your method satisfies what the teacher needs, namely give an estimate of the value, and be able to state whether the exact answer is higher or lower than your estimate.
If you want to have a closer estimate (or even the exact answer), here's what I would do, knowing that you already know how to multiply a number by 11 mentally.
54*23
=55*23 - 1*23
=11*(23*5) - 23
=11*115 - 23
=1265 -23
1265 is the estimate, it is an over estimate.
The exact answer can also be calculated mentally as 1265-23=1242
Note: To multiply a number by 5, add a zero and divide by 2.
23*5 = 230/2 =115
To estimate the expression 54 * 23, you can round each number to a more manageable value and then perform the multiplication. In this case, you rounded 54 to 50 and 23 to 20.
You then calculated the estimate by multiplying 50 and 20, which resulted in 1000.
To determine whether the exact answer is greater or less than the estimate, you compared the estimate with the exact answer, which is 1242.
Since the exact answer, 1242, is greater than the estimate, 1000, you concluded that the exact answer is greater than the estimate.
It's important to note that when rounding, the accuracy of the estimate may vary, depending on the level of precision required. In this case, rounding to the nearest tens place was appropriate for a rough estimate.