# HelpBasic math

1. Jan 27, 2006

### Gamma

I am new to this type of math. I need help.............

Can any one point to me to a good web site where I can learn about rounding and stuff.

Here is another one I am struggling with. I looked in the internet could not find one that really explains it well

How to estimated 3.9 * 7.4 using front end rounding?

How to estimated 33.294/6.2, again using front end rounding?

Arrange in assending order the following: 0.321,0.302,8/25

This one look straight forward as 8/25 = 0.32 --> 0.302, 8/25, 0.321
But if I am mindful about sig figures 8/25 = 0.3 and my assending order becomes, 8/25,0.302, 0.321.

Any help or hint is much appreciated.

Thanks,

gamma.

2. Jan 28, 2006

### HallsofIvy

Staff Emeritus
I doubt you need a whole web site for that! "Front end rounding" just means round to the nearest one digit number. Since 3.9 is closer to 4 than to 3 (since 9> 5) it rounds to 4. 7.4 rounds to 7. What is 4*7?

Same idea. 33.294 rounds to 30, 6.2 to 6. What is 30/6?

Good! That's exactly right!

No. "significant figures" is only used with approximate figures (like measurements). The integers in a fraction are never approximate. You could think of 8/25 as 8.0000/25.0000 is you like. The correct order is
0.302, 8/25, 0.321 as you gave before.

3. Jan 28, 2006

### Gamma

nicely explained.... thank you HallsofIvy. These stuff were not in our curriculum during my school days (not usa) and that is hunting me now.

Thanks,

Gamma.

4. Jan 29, 2006

### t!m

Mm, I'd be careful with front-end rounding. There's really no 'standard' way to do it, but it certainly is not your basic rules for rounding, i.e. >5 rounds up. The most common, and simple way, I remember being taught front-end rounding was to simply use the first digit of each number, hence front-end.

For 3.9*7.4, I would bet that this is meant to be 3*7, using front-end. It certainly isn't an accurate approximation, but it's a fast one, and one that I remember being taught.

There are all kinds of 'correction' techniques, but that would vary by the curriculum.