Question

If a thickness of a paper is 9 x10 ^ -3 Cm then how many sheets of paper are in a book of 5 cm thick.

Answer 1

5cm = 5 x 10^0 cm.

So how many times would 9 x 10^-3 go into 5 x 10^0?

Answer 2

1.8 x 10 ^ -3

Answer 3

Close, but you're dividing the wrong way.

Answer 4

so i would have to divide 5 by 9

Answer 5

which would be 5.5 (bar notation)

Answer 6

There's a rule for dividing exponents:

\[\Large \frac{{{x^n}}}{{{x^m}}} = {x^{n - m}}\]
So:
\[\Large \begin{array}{l}
\frac{{5 \times {{10}^0}}}{{9 \times {{10}^{ - 3}}}} = \frac{5}{9} \times {10^{0 - - 3}} = \frac{5}{9} \times {10^3}\\\\\\
\cong 5.56 \times {10^2}
\end{array}\]

Answer 7

yes but how did you get the 10 ^ 3 to 10^ 2

Answer 8

5/9 is about 0.556. So 0.556 x 10^3 = 5.56 x 10^2 = 55.6 x 10^1 = 556 x 10^0.
When you go down another factor of 10, you move the decimal place one spot to left; if you go up, then one spot to the right.

Make sense?

Answer 9

Oh okay thanks!

Answer 10

No worries =)