JAMB 1988 · UME · Q11

The thickness of an 800-page book is 18 mm. Calculate the thickness of one leaf of the book, giving your answer in metres and in standard form.

Worked solution (try it first)

Each leaf has a page on each side, so 800 pages make $800 \div 2 = 400$ leaves.
One leaf is $18 \div 400 = 0.045$ mm thick.
Divide by 1000 to change mm to metres: $0.000045$ m, which is $4.50 \times 10^{-5}$ m, option D.