Posted by **B.B.** on Tuesday, June 9, 2009 at 7:55pm.

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.

- Math -
**MathMate**, Tuesday, June 9, 2009 at 10:51pm
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

## Answer This Question

## Related Questions

- Math - I need some help. Here is the problem: Give an estimate for the following...
- Math - I cannot figure this problem out. I have did it several ways and get ...
- statistics - Give an estimate for each expression in Exercises, Then state ...
- Math - Here is the original question: Give an estimate for the following ...
- Math - Here is the question: Find the exact value of the following expression: 6...
- calculus - consider the initial value problem dy/dx=y^2+1, y(0)=0. estimate y(2...
- Math - Explain how you can tell if your estimate answer is greater or less than ...
- Math - if you use $63.00 divided by 9 to estimate $62.59 divided by 9 $7.00 ...
- math - how do you estimate fractions? I know how to estimate numbers and ...
- Calculus - Can someone explain this question to me? What intervals should I use ...

More Related Questions