Question 507457
Round off the numbers to 1 significant digit and then estimate the value of the following expression without using a calculator. Show your work, writing your answer in scientific notation.
<pre>
(287,900,001,000)*(168,000)=a*10^k 

where a=___ and k=___

You round 287,900,001,000 to 300,000,000,000 which is 3×10<sup>11</sup>
You round 168,000 to 200,000 which is 2×10<sup>5</sup>

So you have to multiply 3×10<sup>11</sup> by 2×10<sup>5</sup>
so you multiply the 3 by the 2 getting 6 and add the exponents of 10, 
getting 11+5 or 16.  So a = 6 and k = 16. 

So you get 6×10<sup>16</sup>.

Edwin</pre>