scientific notations

[booxx]

Hey guys. Wonder if you can help me. I dont expect answers but im struggling on significant figures and scientific notations.

 

The figure i have come up with as being the answer is 136500000

 

I need to put this to 2 significant figures and also use scientific notation in my answer.

can someone please help me. It would be much appreciated.

 

Claire

[DrP]

Well - what are the two most prominent figures here? You'll have to round up in this case to the nearest whole number in the second figure.

 

So - you have 136 million 500 thousand. That rounds up to 140 million using the two most significant figures no? (the 1 and the 4) You then have 140,000,000 which in scientific notation, or standard form, gives you 1.4 x 10 to the power of the number decimal places need to get 1.4 back to 140 million. Which is eight decimal places if you count them...

 

So 136,500,000 = 1.4 x 10^8 to 2 significant figures in standard form.

 

 

 

So with that in mind boox - what would it be to 3 SF and 4SF?

 

 

 

(PS - you ony need to ask the question once...)

[booxx]

Thankyou so much.

I do understand most of what you have said. Im only just getting my head around this science stuff but the mathematics part is the bane of my life at the moment. Im sooo confused with it all.

Claire

 

Ok, gonna have a go here DrP

 

So, if 1 and 4 is 2 sig fig of 136,500,00

then 3 sig fig would be 137

then 4 sig fig would be 1365

 

have no idea if im fighting a losing battle here or not

[DrP]

That's right!! you've got it.

 

so in standard form they would be:

1.37 x 10^8 to 3sf's and 1.365 x 10^8 to 4 sf's.

[mooeypoo]

I was thinking that maybe this concept will help you make sense of it, Booxx:

 

I always had a "trick" that I used to remember these (I am used to working with dots moving around, since I was educated on the metric system, and that's how you convert units there, mainly):

 

 

• The significant number will always be the first digit, dot, and however many digits left for the SF, rounded properly, of course (1.4 --> 2 SF, 1.37 --> 3 SF, etc)
  
• The dot, though, is not there originally. It "jumped" places from the beginning of the number to the digit before last (The original number can be written as 136,500,000.0 - hence the dot is at the end...). How many places did it jump? 8 places, which is the number that is the power of the 10.
  

 

It might sound silly, but it helped me remember how to convert to SF back and forth without mixing up my meters, centimeters and milimeters (all related to one another by powers of 10!)

 

Hope that helped

 

~moo

[DrP]

That is exactly how I lernt it as well! We counted the places the dots 'jumped' - and acually marked their little jumps with a pencil above the figure - I wasn't sure how to explain that in writing but you seem to have done it quite well moo.

[mooeypoo]

Metric system rules, DrP