# Math

posted by .

I need help with this problem. The question is : Find the exact value of the following expression. 6*22*5. Use any mental calculation technique you choose. Name the technique you use in each case. Here is what I have:
60*(20+2)*5 but this is where I get stumped. Can someone explain this to me. Thanks.

• Math -

I will show some examples and leave it to you to digest. If more explanations are needed, post again.

Multiply without carry
6*22*5
=(6*5)*22
=30*22
=10*(3*22)
=660

Double and half
6*22*5
=6*(22*5)
=6*(22/2)*(5*2)
=6*11*10
=660

Multiply simple numbers by 11
6*22*5
=(6*5)*2*11
=(30*2)*11
=60*11
=660

• Math -

mathmate you are a really smart person

• Math -

Isn't it amazing what brains, lots of hard work, and a good education can do for a person! :-)

• Math -

Thank you both for the nice comments. I love mental arithmetic, and it's one of my soft spots.

Since it seems to arouse some interest, I will complete the explanation of the third one (multiplication by 11):

When we multiply by 11, we only have to add adjacent digits. It's easier if there is no carry, but it can be done too. I will give an example:
Pretend there is a imaginary zero before the first digit and after the last:
135*11
=(0)135(0)*11
=(0)+1 || 1+3 || 3+5 || 5+0
= 1 || 4 || 8 || 5
= 1485

With a little practice, you can do this without pen and paper.

Try
24513 * 11
= 269643

## Similar Questions

1. ### FACTORING

I can't figure out how to factor this. I know you use the technique Factor by Grouping. But can someone explain to me how to factor this problem by using factor by grouping technique. Problem: 30x^3 + 18x^2 - 5x - 3. Thanks so much:) …
2. ### Math

Here is the original question: Give an estimate for the following expression: 978*66. Is the exact answer going to be greater than or less than the estimate?
3. ### Math

Here is the question: Find the exact value of the following expression: 6*22*5. Use any mental calculation technique you choose. Name the technique. Here is what my answer looks like: 6*22*5 (6*5)*2*11 (30*2)*11 60*11=660 I multiplied …
4. ### Math

Solve the quadratic equation using any technique you wish. Name the technique. Check. 12x2 + 10x = 0
5. ### Math

Solve the linear equation using any technique you have learned. Name the technique. Check. 3x + 12 = -7x - 28
6. ### Math

Solve the quadratic equation using any technique you wish. Name the technique. Check. 12x2 + 10x = 0
7. ### Math

Solve the linear equation using any technique you have learned. Name the technique. Check. 3x + 12 = -7x - 28
8. ### Math

Solve the quadratic equation using any technique you wish. Name the technique. Check. 12x2 + 10x = 0
9. ### algebra

Solve the linear equation using any technique you have learned. Name the technique. Check. 3x + 12 = -7x - 28 I know the answer is x = -4 and I know that substitution is the technique that is used, but I can't figure out how to set …
10. ### social science

suppose your sociology instructor has asked you to do a study of homelessness. which research technique (survey, observation, experiment, oe ex isting resource) would you use that technique to complete your assignment?

More Similar Questions