Answer:
[tex]1.4*10^9[/tex] cells
Step-by-step explanation:
Let the number of cells she used in 2nd experiment be "x"
Since the latter experiment she uses LESS, we can say:
"What number times 2000 gives us 2.8 * 10 ^ 12??"
We can create an equation such as:
[tex]x*2000=2.8*10^{12}[/tex]
Thus, x would be:
[tex]x*2000=2.8*10^{12}\\x=\frac{2.8*10^{12}}{2000}[/tex]
Let's convert 2000 into scientific notation first. We would take decimal point to the left until we have 1 digit to left of decimal and make 10 raised to that many units we take left "to the power".
So
2000 = 2 * 10 ^3
Now, let's remember rule of dividing numbers in scientific notation:
[tex]\frac{a*10^b}{c*10^d}=(\frac{a}{c})*10^{b-d}[/tex]
Now, we do our problem using this rule:
[tex]x=\frac{2.8*10^{12}}{2000}\\x=\frac{2.8*10^{12}}{2*10^3}\\x=(\frac{2.8}{2})*10^{12-3}\\x=1.4*10^9[/tex]
Thus, she used [tex]1.4*10^9[/tex] cells in her 2nd experiment